#1617 update license headers

.checkstyle files are being tracked which should not be

.all-contributorsrc

@@ -315,7 +315,8 @@
       "avatar_url": "https://avatars1.githubusercontent.com/u/6295975?v=4",
       "profile": "https://github.com/Anurag870",
       "contributions": [
-        "code"
+        "code",
+        "doc"
       ]
     },
     {
@@ -946,7 +947,8 @@
       "avatar_url": "https://avatars3.githubusercontent.com/u/23739158?v=4",
       "profile": "https://github.com/grzesiekkedzior",
       "contributions": [
-        "code"
+        "code",
+        "review"
       ]
     },
     {
@@ -1082,7 +1084,8 @@
       "avatar_url": "https://avatars1.githubusercontent.com/u/10645273?v=4",
       "profile": "https://github.com/ravening",
       "contributions": [
-        "code"
+        "code",
+        "review"
       ]
     },
     {
@@ -1149,6 +1152,231 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "edycutjong",
+      "name": "Edy Cu Tjong",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/1098102?v=4",
+      "profile": "http://www.edycutjong.com",
+      "contributions": [
+        "doc"
+      ]
+    },
+    {
+      "login": "mkrzywanski",
+      "name": "Michał Krzywański",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/15279585?v=4",
+      "profile": "https://github.com/mkrzywanski",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "stefanbirkner",
+      "name": "Stefan Birkner",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/711349?v=4",
+      "profile": "https://www.stefan-birkner.de",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "fedorskvorcov",
+      "name": "Fedor Skvorcov",
+      "avatar_url": "https://avatars3.githubusercontent.com/u/43882212?v=4",
+      "profile": "https://github.com/fedorskvorcov",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "samilAyoub",
+      "name": "samilAyoub",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/61546990?v=4",
+      "profile": "https://github.com/samilAyoub",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "vdlald",
+      "name": "Vladislav Golubinov",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/29997701?v=4",
+      "profile": "https://github.com/vdlald",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "swarajsaaj",
+      "name": "Swaraj",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/6285049?v=4",
+      "profile": "https://github.com/swarajsaaj",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "ChFlick",
+      "name": "Christoph Flick",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/4465376?v=4",
+      "profile": "http://christophflick.de",
+      "contributions": [
+        "doc"
+      ]
+    },
+    {
+      "login": "Ascenio",
+      "name": "Ascênio",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/7662016?v=4",
+      "profile": "https://github.com/Ascenio",
+      "contributions": [
+        "review"
+      ]
+    },
+    {
+      "login": "dsibilio",
+      "name": "Domenico Sibilio",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/24280982?v=4",
+      "profile": "https://www.linkedin.com/in/domenico-sibilio/",
+      "contributions": [
+        "doc"
+      ]
+    },
+    {
+      "login": "akashchandwani",
+      "name": "Akash Chandwani",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/3483277?v=4",
+      "profile": "https://github.com/akashchandwani",
+      "contributions": [
+        "review"
+      ]
+    },
+    {
+      "login": "manannikov",
+      "name": "Pavlo Manannikov",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/7019769?v=4",
+      "profile": "http://www.linkedin.com/in/manannikov",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "eimanip",
+      "name": "Eiman",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/20307301?v=4",
+      "profile": "https://github.com/eimanip",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "OrangePants-R",
+      "name": "Rocky",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/42976136?v=4",
+      "profile": "https://github.com/OrangePants-R",
+      "contributions": [
+        "doc"
+      ]
+    },
+    {
+      "login": "ibrahimAlii",
+      "name": "Ibrahim ali abdelghany",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/21141301?v=4",
+      "profile": "https://ibrahimalii.github.io/",
+      "contributions": [
+        "review"
+      ]
+    },
+    {
+      "login": "gkulkarni2020",
+      "name": "Girish Kulkarni",
+      "avatar_url": "https://avatars3.githubusercontent.com/u/5161548?v=4",
+      "profile": "https://github.com/gkulkarni2020",
+      "contributions": [
+        "doc"
+      ]
+    },
+    {
+      "login": "omk13",
+      "name": "Omar Karazoun",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/59054172?v=4",
+      "profile": "https://github.com/omk13",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "jeff303",
+      "name": "Jeff Evans",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/3521562?v=4",
+      "profile": "https://github.com/jeff303",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "viveksb007",
+      "name": "Vivek Singh",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/12713808?v=4",
+      "profile": "https://viveksb007.github.io",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "siavashsoleymani",
+      "name": "siavash",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/18074419?v=4",
+      "profile": "https://github.com/siavashsoleymani",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "ruchpeanuts",
+      "name": "ruchpeanuts",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/29301900?v=4",
+      "profile": "https://github.com/ruchpeanuts",
+      "contributions": [
+        "doc"
+      ]
+    },
+    {
+      "login": "warp125",
+      "name": "warp125",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/48073115?v=4",
+      "profile": "https://github.com/warp125",
+      "contributions": [
+        "translation"
+      ]
+    },
+    {
+      "login": "tkhadir",
+      "name": "KHADIR Tayeb",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/45130488?v=4",
+      "profile": "http://libkhadir.fr",
+      "contributions": [
+        "translation"
+      ]
+    },
+    {
+      "login": "ignite1771",
+      "name": "ignite1771",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/59446563?v=4",
+      "profile": "https://github.com/ignite1771",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "demirhalil",
+      "name": "Halil Demir",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/22895118?v=4",
+      "profile": "https://github.com/demirhalil",
+      "contributions": [
+        "translation"
+      ]
     }
   ],
   "contributorsPerLine": 4,

.github/workflows/maven-ci.yml

@@ -30,35 +30,51 @@ on:
   push:
     branches: [ master ]
 
+
 jobs:
+
   build:
 
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@v2
+
+    - name: Checkout Code
+      uses: actions/checkout@v2
+      with:
+        # Disabling shallow clone for improving relevancy of SonarQube reporting
+        fetch-depth: 0
+
     - name: Set up JDK 11
       uses: actions/setup-java@v1
       with:
         java-version: 11
-    - uses: actions/cache@v2
+
+    - name: Cache SonarCloud packages
+      uses: actions/cache@v2
+      with:
+        path: ~/.sonar/cache
+        key: ${{ runner.os }}-sonar
+        restore-keys: ${{ runner.os }}-sonar
+
+    - name: Cache Maven dependencies
+      uses: actions/cache@v2
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
         restore-keys: |
           ${{ runner.os }}-maven-
+
     # Some tests need screen access
     - name: Install xvfb
-      run: sudo apt-get install xvfb
-    # SonarQube scan does not work for forked repositories
+      run: sudo apt-get install -y xvfb
+
+    # The SonarQube analysis is only for the master branch of the main repository.
+    # SonarQube scan does not work for forked repositories try changing it to xvfb-run mvn clean verify
     # See https://jira.sonarsource.com/browse/MMF-1371
-    - name: Build with Maven
-      if: github.ref != 'refs/heads/master'
-      run: xvfb-run mvn clean verify
     - name: Build with Maven and run SonarQube analysis
-      if: github.ref == 'refs/heads/master'
       run: xvfb-run mvn clean verify org.sonarsource.scanner.maven:sonar-maven-plugin:sonar
       env:
         # These two env variables are needed for sonar analysis
-        GITHUB_TOKEN: ${{ secrets.REPOSITORY_ACCESS_TOKEN }}
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

.github/workflows/maven-pr-builder.yml

@@ -29,29 +29,36 @@ name: Java PR Builder
 on:
   pull_request:
     branches: [ master ]
+    types: [ opened, reopened, synchronize, labeled, unlabeled ]
 
 jobs:
   build:
 
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@v2
+    - name: Checkout Code
+      uses: actions/checkout@v2
+    
     - name: Set up JDK 11
       uses: actions/setup-java@v1
       with:
         java-version: 11
-    - uses: actions/cache@v2
+    
+    - name: Cache Maven Dependecies
+      uses: actions/cache@v2
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
         restore-keys: |
           ${{ runner.os }}-maven-
+    
     # Some tests need screen access
     - name: Install xvfb
-      run: sudo apt-get install xvfb
-    # SonarQube scan does not work for forked repositories
+      run: sudo apt-get install -y xvfb
+    
+    # This worflow is only for building Pull Requests, the master branch runs Sonar analysis on the main repository.
+    # SonarQube scan does not work for forked repositories.
     # See https://jira.sonarsource.com/browse/MMF-1371
     - name: Build with Maven
-      if: github.ref != 'refs/heads/master'
       run: xvfb-run mvn clean verify

.gitignore

@@ -4,7 +4,8 @@ target
 .classpath
 .project
 *.class
-# Package Files #
+
+### Package Files ###
 *.jar
 *.war
 *.ear
@@ -13,7 +14,8 @@ target
 *.swp
 datanucleus.log
 /bin/
-/bin/
-/bin/
 *.log
 event-sourcing/Journal.json
+
+### Checkstyle ###
+.checkstyle

README.md

@@ -6,12 +6,19 @@
 
 ![Java CI with Maven](https://github.com/iluwatar/java-design-patterns/workflows/Java%20CI%20with%20Maven/badge.svg)
 [![License MIT](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/iluwatar/java-design-patterns/master/LICENSE.md)
+[![Lines of Code](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=ncloc)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns) 
+[![Coverage](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=coverage)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
 [![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
-[![Sonarcloud Status](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=alert_status)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns) 
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-126-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-151-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
+<br/>
+
+Read in different language : [![CN](/assets/flags/CN.png)**CN**](/zh/README.md),[![KR](/assets/flags/KR.png)**KR**](/ko/README.md),[![FR](/assets/flags/FR.png)**FR**](/fr/README.md),[![TR](/assets/flags/TR.png)**TR**](/tr/README.md),
+
+<br/>
+
 # Introduction
 
 Design patterns are the best formalized practices a programmer can use to
@@ -30,7 +37,7 @@ This site showcases Java Design Patterns. The solutions have been developed by
 experienced programmers and architects from the open source community. The 
 patterns can be browsed by their high level descriptions or by looking at their
 source code. The source code examples are well commented and can be thought as
-programming tutorials how to implement a specific pattern. We use the most
+programming tutorials on how to implement a specific pattern. We use the most
 popular battle-proven open source Java technologies.
 
 Before you dive into the material, you should be familiar with various
@@ -69,197 +76,235 @@ This project is licensed under the terms of the MIT license.
 <!-- markdownlint-disable -->
 <table>
   <tr>
-    <td align="center"><a href="https://github.com/iluwatar"><img src="https://avatars1.githubusercontent.com/u/582346?v=4" width="100px;" alt=""/><br /><sub><b>Ilkka Seppälä</b></sub></a><br /><a href="#projectManagement-iluwatar" title="Project Management">📆</a> <a href="#maintenance-iluwatar" title="Maintenance">🚧</a> <a href="#content-iluwatar" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/amit1307"><img src="https://avatars0.githubusercontent.com/u/23420222?v=4" width="100px;" alt=""/><br /><sub><b>amit1307</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amit1307" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/npathai"><img src="https://avatars2.githubusercontent.com/u/1792515?v=4" width="100px;" alt=""/><br /><sub><b>Narendra Pathai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=npathai" title="Code">💻</a> <a href="#ideas-npathai" title="Ideas, Planning, & Feedback">🤔</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Anpathai" title="Reviewed Pull Requests">👀</a></td>
-    <td align="center"><a href="https://github.com/fluxw42"><img src="https://avatars1.githubusercontent.com/u/1545460?v=4" width="100px;" alt=""/><br /><sub><b>Jeroen Meulemeester</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fluxw42" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/iluwatar"><img src="https://avatars1.githubusercontent.com/u/582346?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ilkka Seppälä</b></sub></a><br /><a href="#projectManagement-iluwatar" title="Project Management">📆</a> <a href="#maintenance-iluwatar" title="Maintenance">🚧</a> <a href="#content-iluwatar" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/amit1307"><img src="https://avatars0.githubusercontent.com/u/23420222?v=4?s=100" width="100px;" alt=""/><br /><sub><b>amit1307</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amit1307" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/npathai"><img src="https://avatars2.githubusercontent.com/u/1792515?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Narendra Pathai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=npathai" title="Code">💻</a> <a href="#ideas-npathai" title="Ideas, Planning, & Feedback">🤔</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Anpathai" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://github.com/fluxw42"><img src="https://avatars1.githubusercontent.com/u/1545460?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jeroen Meulemeester</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fluxw42" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="http://www.joemccarthy.co.uk"><img src="https://avatars0.githubusercontent.com/u/4526195?v=4" width="100px;" alt=""/><br /><sub><b>Joseph McCarthy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mikulucky" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/thomasoss"><img src="https://avatars1.githubusercontent.com/u/22516154?v=4" width="100px;" alt=""/><br /><sub><b>Thomas</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=thomasoss" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/anuragagarwal561994"><img src="https://avatars1.githubusercontent.com/u/6075379?v=4" width="100px;" alt=""/><br /><sub><b>Anurag Agarwal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=anuragagarwal561994" title="Code">💻</a></td>
-    <td align="center"><a href="https://markusmo3.github.io"><img src="https://avatars1.githubusercontent.com/u/3317416?v=4" width="100px;" alt=""/><br /><sub><b>Markus Moser</b></sub></a><br /><a href="#design-markusmo3" title="Design">🎨</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=markusmo3" title="Code">💻</a> <a href="#ideas-markusmo3" title="Ideas, Planning, & Feedback">🤔</a></td>
+    <td align="center"><a href="http://www.joemccarthy.co.uk"><img src="https://avatars0.githubusercontent.com/u/4526195?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Joseph McCarthy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mikulucky" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/thomasoss"><img src="https://avatars1.githubusercontent.com/u/22516154?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Thomas</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=thomasoss" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/anuragagarwal561994"><img src="https://avatars1.githubusercontent.com/u/6075379?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Anurag Agarwal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=anuragagarwal561994" title="Code">💻</a></td>
+    <td align="center"><a href="https://markusmo3.github.io"><img src="https://avatars1.githubusercontent.com/u/3317416?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Markus Moser</b></sub></a><br /><a href="#design-markusmo3" title="Design">🎨</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=markusmo3" title="Code">💻</a> <a href="#ideas-markusmo3" title="Ideas, Planning, & Feedback">🤔</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://twitter.com/i_sabiq"><img src="https://avatars1.githubusercontent.com/u/19510920?v=4" width="100px;" alt=""/><br /><sub><b>Sabiq Ihab</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=isabiq" title="Code">💻</a></td>
-    <td align="center"><a href="http://inbravo.github.io"><img src="https://avatars3.githubusercontent.com/u/5253764?v=4" width="100px;" alt=""/><br /><sub><b>Amit Dixit</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=inbravo" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/piyushchaudhari04"><img src="https://avatars3.githubusercontent.com/u/10268029?v=4" width="100px;" alt=""/><br /><sub><b>Piyush Kailash Chaudhari</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=piyushchaudhari04" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/joshzambales"><img src="https://avatars1.githubusercontent.com/u/8704552?v=4" width="100px;" alt=""/><br /><sub><b>joshzambales</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=joshzambales" title="Code">💻</a></td>
+    <td align="center"><a href="https://twitter.com/i_sabiq"><img src="https://avatars1.githubusercontent.com/u/19510920?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sabiq Ihab</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=isabiq" title="Code">💻</a></td>
+    <td align="center"><a href="http://inbravo.github.io"><img src="https://avatars3.githubusercontent.com/u/5253764?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Amit Dixit</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=inbravo" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/piyushchaudhari04"><img src="https://avatars3.githubusercontent.com/u/10268029?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Piyush Kailash Chaudhari</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=piyushchaudhari04" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/joshzambales"><img src="https://avatars1.githubusercontent.com/u/8704552?v=4?s=100" width="100px;" alt=""/><br /><sub><b>joshzambales</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=joshzambales" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/Crossy147"><img src="https://avatars2.githubusercontent.com/u/7272996?v=4" width="100px;" alt=""/><br /><sub><b>Kamil Pietruszka</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Crossy147" title="Code">💻</a></td>
-    <td align="center"><a href="http://cs.joensuu.fi/~zkhayda"><img src="https://avatars2.githubusercontent.com/u/660742?v=4" width="100px;" alt=""/><br /><sub><b>Zafar Khaydarov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Documentation">📖</a></td>
-    <td align="center"><a href="https://kemitix.github.io/"><img src="https://avatars1.githubusercontent.com/u/1147749?v=4" width="100px;" alt=""/><br /><sub><b>Paul Campbell</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kemitix" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/Argyro-Sioziou"><img src="https://avatars0.githubusercontent.com/u/22822639?v=4" width="100px;" alt=""/><br /><sub><b>Argyro Sioziou</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Argyro-Sioziou" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Crossy147"><img src="https://avatars2.githubusercontent.com/u/7272996?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kamil Pietruszka</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Crossy147" title="Code">💻</a></td>
+    <td align="center"><a href="http://cs.joensuu.fi/~zkhayda"><img src="https://avatars2.githubusercontent.com/u/660742?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Zafar Khaydarov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://kemitix.github.io/"><img src="https://avatars1.githubusercontent.com/u/1147749?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Paul Campbell</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kemitix" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Argyro-Sioziou"><img src="https://avatars0.githubusercontent.com/u/22822639?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Argyro Sioziou</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Argyro-Sioziou" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/TylerMcConville"><img src="https://avatars0.githubusercontent.com/u/4946449?v=4" width="100px;" alt=""/><br /><sub><b>TylerMcConville</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=TylerMcConville" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/saksham93"><img src="https://avatars1.githubusercontent.com/u/37399540?v=4" width="100px;" alt=""/><br /><sub><b>saksham93</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=saksham93" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/nikhilbarar"><img src="https://avatars2.githubusercontent.com/u/37332144?v=4" width="100px;" alt=""/><br /><sub><b>nikhilbarar</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nikhilbarar" title="Code">💻</a></td>
-    <td align="center"><a href="http://colinbut.com"><img src="https://avatars2.githubusercontent.com/u/10725674?v=4" width="100px;" alt=""/><br /><sub><b>Colin But</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=colinbut" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/TylerMcConville"><img src="https://avatars0.githubusercontent.com/u/4946449?v=4?s=100" width="100px;" alt=""/><br /><sub><b>TylerMcConville</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=TylerMcConville" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/saksham93"><img src="https://avatars1.githubusercontent.com/u/37399540?v=4?s=100" width="100px;" alt=""/><br /><sub><b>saksham93</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=saksham93" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/nikhilbarar"><img src="https://avatars2.githubusercontent.com/u/37332144?v=4?s=100" width="100px;" alt=""/><br /><sub><b>nikhilbarar</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nikhilbarar" title="Code">💻</a></td>
+    <td align="center"><a href="http://colinbut.com"><img src="https://avatars2.githubusercontent.com/u/10725674?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Colin But</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=colinbut" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/ruslanpa"><img src="https://avatars2.githubusercontent.com/u/1503411?v=4" width="100px;" alt=""/><br /><sub><b>Ruslan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ruslanpa" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/JuhoKang"><img src="https://avatars1.githubusercontent.com/u/4745294?v=4" width="100px;" alt=""/><br /><sub><b>Juho Kang</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=JuhoKang" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/dheeraj-mummareddy"><img src="https://avatars2.githubusercontent.com/u/7002230?v=4" width="100px;" alt=""/><br /><sub><b>Dheeraj Mummareddy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dheeraj-mummareddy" title="Code">💻</a></td>
-    <td align="center"><a href="https://www.bernardosulzbach.com"><img src="https://avatars0.githubusercontent.com/u/8271090?v=4" width="100px;" alt=""/><br /><sub><b>Bernardo Sulzbach</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=bernardosulzbach" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ruslanpa"><img src="https://avatars2.githubusercontent.com/u/1503411?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ruslan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ruslanpa" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/JuhoKang"><img src="https://avatars1.githubusercontent.com/u/4745294?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Juho Kang</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=JuhoKang" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/dheeraj-mummareddy"><img src="https://avatars2.githubusercontent.com/u/7002230?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dheeraj Mummareddy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dheeraj-mummareddy" title="Code">💻</a></td>
+    <td align="center"><a href="https://www.bernardosulzbach.com"><img src="https://avatars0.githubusercontent.com/u/8271090?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Bernardo Sulzbach</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=bernardosulzbach" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/4lexis"><img src="https://avatars0.githubusercontent.com/u/19871727?v=4" width="100px;" alt=""/><br /><sub><b>Aleksandar Dudukovic</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=4lexis" title="Code">💻</a></td>
-    <td align="center"><a href="https://www.yusufaytas.com"><img src="https://avatars2.githubusercontent.com/u/1049483?v=4" width="100px;" alt=""/><br /><sub><b>Yusuf Aytaş</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yusufaytas" title="Code">💻</a></td>
-    <td align="center"><a href="http://futurehomes.hu"><img src="https://avatars2.githubusercontent.com/u/1001491?v=4" width="100px;" alt=""/><br /><sub><b>Mihály Kuprivecz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qpi" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/kapinuss"><img src="https://avatars0.githubusercontent.com/u/17639945?v=4" width="100px;" alt=""/><br /><sub><b>Stanislav Kapinus</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kapinuss" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/4lexis"><img src="https://avatars0.githubusercontent.com/u/19871727?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Aleksandar Dudukovic</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=4lexis" title="Code">💻</a></td>
+    <td align="center"><a href="https://www.yusufaytas.com"><img src="https://avatars2.githubusercontent.com/u/1049483?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Yusuf Aytaş</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yusufaytas" title="Code">💻</a></td>
+    <td align="center"><a href="http://futurehomes.hu"><img src="https://avatars2.githubusercontent.com/u/1001491?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mihály Kuprivecz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qpi" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/kapinuss"><img src="https://avatars0.githubusercontent.com/u/17639945?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Stanislav Kapinus</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kapinuss" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/gvsharma"><img src="https://avatars1.githubusercontent.com/u/6648152?v=4" width="100px;" alt=""/><br /><sub><b>GVSharma</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gvsharma" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/SrdjanPaunovic"><img src="https://avatars1.githubusercontent.com/u/22815104?v=4" width="100px;" alt=""/><br /><sub><b>Srđan Paunović</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=SrdjanPaunovic" title="Code">💻</a></td>
-    <td align="center"><a href="https://sideris.xyz/"><img src="https://avatars3.githubusercontent.com/u/5484694?v=4" width="100px;" alt=""/><br /><sub><b>Petros G. Sideris</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=sideris" title="Code">💻</a></td>
-    <td align="center"><a href="https://www.linkedin.com/in/pramodgupta3/"><img src="https://avatars1.githubusercontent.com/u/2184241?v=4" width="100px;" alt=""/><br /><sub><b>Pramod Gupta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AIAmPramod" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://github.com/gvsharma"><img src="https://avatars1.githubusercontent.com/u/6648152?v=4?s=100" width="100px;" alt=""/><br /><sub><b>GVSharma</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gvsharma" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/SrdjanPaunovic"><img src="https://avatars1.githubusercontent.com/u/22815104?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Srđan Paunović</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=SrdjanPaunovic" title="Code">💻</a></td>
+    <td align="center"><a href="https://sideris.xyz/"><img src="https://avatars3.githubusercontent.com/u/5484694?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Petros G. Sideris</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=sideris" title="Code">💻</a></td>
+    <td align="center"><a href="https://www.linkedin.com/in/pramodgupta3/"><img src="https://avatars1.githubusercontent.com/u/2184241?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Pramod Gupta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AIAmPramod" title="Reviewed Pull Requests">👀</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://amarnath510.github.io/portfolio"><img src="https://avatars0.githubusercontent.com/u/4599623?v=4" width="100px;" alt=""/><br /><sub><b>Amarnath Chandana</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Amarnath510" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/Anurag870"><img src="https://avatars1.githubusercontent.com/u/6295975?v=4" width="100px;" alt=""/><br /><sub><b>Anurag870</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Anurag870" title="Code">💻</a></td>
-    <td align="center"><a href="http://theerroris.me"><img src="https://avatars0.githubusercontent.com/u/1685953?v=4" width="100px;" alt=""/><br /><sub><b>Wes Gilleland</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Deathnerd" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/Harshrajsinh"><img src="https://avatars2.githubusercontent.com/u/22811531?v=4" width="100px;" alt=""/><br /><sub><b>Harshraj Thakor</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Harshrajsinh" title="Code">💻</a></td>
+    <td align="center"><a href="https://amarnath510.github.io/portfolio"><img src="https://avatars0.githubusercontent.com/u/4599623?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Amarnath Chandana</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Amarnath510" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Anurag870"><img src="https://avatars1.githubusercontent.com/u/6295975?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Anurag870</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Anurag870" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=Anurag870" title="Documentation">📖</a></td>
+    <td align="center"><a href="http://theerroris.me"><img src="https://avatars0.githubusercontent.com/u/1685953?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Wes Gilleland</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Deathnerd" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Harshrajsinh"><img src="https://avatars2.githubusercontent.com/u/22811531?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Harshraj Thakor</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Harshrajsinh" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/MaVdbussche"><img src="https://avatars1.githubusercontent.com/u/26136934?v=4" width="100px;" alt=""/><br /><sub><b>Martin Vandenbussche</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=MaVdbussche" title="Code">💻</a></td>
-    <td align="center"><a href="https://alexsomai.com"><img src="https://avatars1.githubusercontent.com/u/5720977?v=4" width="100px;" alt=""/><br /><sub><b>Alexandru Somai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=alexsomai" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/amogozov"><img src="https://avatars3.githubusercontent.com/u/7372215?v=4" width="100px;" alt=""/><br /><sub><b>Artur Mogozov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amogozov" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/anthonycampbell"><img src="https://avatars3.githubusercontent.com/u/10249255?v=4" width="100px;" alt=""/><br /><sub><b>anthony</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=anthonycampbell" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/MaVdbussche"><img src="https://avatars1.githubusercontent.com/u/26136934?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Martin Vandenbussche</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=MaVdbussche" title="Code">💻</a></td>
+    <td align="center"><a href="https://alexsomai.com"><img src="https://avatars1.githubusercontent.com/u/5720977?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Alexandru Somai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=alexsomai" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/amogozov"><img src="https://avatars3.githubusercontent.com/u/7372215?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Artur Mogozov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amogozov" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/anthonycampbell"><img src="https://avatars3.githubusercontent.com/u/10249255?v=4?s=100" width="100px;" alt=""/><br /><sub><b>anthony</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=anthonycampbell" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="http://ccygnus.com/"><img src="https://avatars1.githubusercontent.com/u/9342724?v=4" width="100px;" alt=""/><br /><sub><b>Christian Cygnus</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=christophercolumbusdog" title="Code">💻</a></td>
-    <td align="center"><a href="https://about.me/dzmitryh"><img src="https://avatars2.githubusercontent.com/u/5390492?v=4" width="100px;" alt=""/><br /><sub><b>Dima Gubin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dzmitryh" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/jjjimenez100"><img src="https://avatars3.githubusercontent.com/u/22243493?v=4" width="100px;" alt=""/><br /><sub><b>Joshua Jimenez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jjjimenez100" title="Code">💻</a></td>
-    <td align="center"><a href="http://about.me/kaiwinter"><img src="https://avatars0.githubusercontent.com/u/110982?v=4" width="100px;" alt=""/><br /><sub><b>Kai Winter</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kaiwinter" title="Code">💻</a></td>
+    <td align="center"><a href="http://ccygnus.com/"><img src="https://avatars1.githubusercontent.com/u/9342724?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christian Cygnus</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=christophercolumbusdog" title="Code">💻</a></td>
+    <td align="center"><a href="https://about.me/dzmitryh"><img src="https://avatars2.githubusercontent.com/u/5390492?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dima Gubin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dzmitryh" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/jjjimenez100"><img src="https://avatars3.githubusercontent.com/u/22243493?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Joshua Jimenez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jjjimenez100" title="Code">💻</a></td>
+    <td align="center"><a href="http://about.me/kaiwinter"><img src="https://avatars0.githubusercontent.com/u/110982?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kai Winter</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kaiwinter" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/lbroman"><img src="https://avatars1.githubusercontent.com/u/86007?v=4" width="100px;" alt=""/><br /><sub><b>lbroman</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=lbroman" title="Code">💻</a></td>
-    <td align="center"><a href="https://przemeknowak.com"><img src="https://avatars1.githubusercontent.com/u/3254609?v=4" width="100px;" alt=""/><br /><sub><b>Przemek</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=pnowy" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/prafful1"><img src="https://avatars0.githubusercontent.com/u/14350274?v=4" width="100px;" alt=""/><br /><sub><b>Prafful Agarwal</b></sub></a><br /><a href="#content-prafful1" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/sankypanhale"><img src="https://avatars1.githubusercontent.com/u/6478783?v=4" width="100px;" alt=""/><br /><sub><b>Sanket Panhale</b></sub></a><br /><a href="#content-sankypanhale" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/lbroman"><img src="https://avatars1.githubusercontent.com/u/86007?v=4?s=100" width="100px;" alt=""/><br /><sub><b>lbroman</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=lbroman" title="Code">💻</a></td>
+    <td align="center"><a href="https://przemeknowak.com"><img src="https://avatars1.githubusercontent.com/u/3254609?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Przemek</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=pnowy" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/prafful1"><img src="https://avatars0.githubusercontent.com/u/14350274?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Prafful Agarwal</b></sub></a><br /><a href="#content-prafful1" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/sankypanhale"><img src="https://avatars1.githubusercontent.com/u/6478783?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sanket Panhale</b></sub></a><br /><a href="#content-sankypanhale" title="Content">🖋</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/staillebois"><img src="https://avatars0.githubusercontent.com/u/23701200?v=4" width="100px;" alt=""/><br /><sub><b>staillebois</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=staillebois" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/valdar-hu"><img src="https://avatars3.githubusercontent.com/u/17962817?v=4" width="100px;" alt=""/><br /><sub><b>Krisztián Nagy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=valdar-hu" title="Code">💻</a></td>
-    <td align="center"><a href="https://www.vanogrid.com"><img src="https://avatars0.githubusercontent.com/u/4307918?v=4" width="100px;" alt=""/><br /><sub><b>Alexander Ivanov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vanogrid" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/yosfik"><img src="https://avatars3.githubusercontent.com/u/4850270?v=4" width="100px;" alt=""/><br /><sub><b>Yosfik Alqadri</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yosfik" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/staillebois"><img src="https://avatars0.githubusercontent.com/u/23701200?v=4?s=100" width="100px;" alt=""/><br /><sub><b>staillebois</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=staillebois" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/valdar-hu"><img src="https://avatars3.githubusercontent.com/u/17962817?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Krisztián Nagy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=valdar-hu" title="Code">💻</a></td>
+    <td align="center"><a href="https://www.vanogrid.com"><img src="https://avatars0.githubusercontent.com/u/4307918?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Alexander Ivanov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vanogrid" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/yosfik"><img src="https://avatars3.githubusercontent.com/u/4850270?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Yosfik Alqadri</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yosfik" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/7agustibm"><img src="https://avatars0.githubusercontent.com/u/8149332?v=4" width="100px;" alt=""/><br /><sub><b>Agustí Becerra Milà</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=7agustibm" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/Juaanma"><img src="https://avatars3.githubusercontent.com/u/7390500?v=4" width="100px;" alt=""/><br /><sub><b>Juan Manuel Suárez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Juaanma" title="Code">💻</a></td>
-    <td align="center"><a href="http://www.devsedge.net/"><img src="https://avatars0.githubusercontent.com/u/9956006?v=4" width="100px;" alt=""/><br /><sub><b>Luigi Cortese</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=LuigiCortese" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/Rzeposlaw"><img src="https://avatars2.githubusercontent.com/u/18425745?v=4" width="100px;" alt=""/><br /><sub><b>Katarzyna Rzepecka</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Rzeposlaw" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/7agustibm"><img src="https://avatars0.githubusercontent.com/u/8149332?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Agustí Becerra Milà</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=7agustibm" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Juaanma"><img src="https://avatars3.githubusercontent.com/u/7390500?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Juan Manuel Suárez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Juaanma" title="Code">💻</a></td>
+    <td align="center"><a href="http://www.devsedge.net/"><img src="https://avatars0.githubusercontent.com/u/9956006?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Luigi Cortese</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=LuigiCortese" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Rzeposlaw"><img src="https://avatars2.githubusercontent.com/u/18425745?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Katarzyna Rzepecka</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Rzeposlaw" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="http://adamski.pro"><img src="https://avatars1.githubusercontent.com/u/6537430?v=4" width="100px;" alt=""/><br /><sub><b>adamski.pro</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=akrystian" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/baislsl"><img src="https://avatars0.githubusercontent.com/u/17060584?v=4" width="100px;" alt=""/><br /><sub><b>Shengli Bai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=baislsl" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/besok"><img src="https://avatars2.githubusercontent.com/u/29834592?v=4" width="100px;" alt=""/><br /><sub><b>Boris</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=besok" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/dmitraver"><img src="https://avatars3.githubusercontent.com/u/1798156?v=4" width="100px;" alt=""/><br /><sub><b>Dmitry Avershin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dmitraver" title="Code">💻</a></td>
+    <td align="center"><a href="http://adamski.pro"><img src="https://avatars1.githubusercontent.com/u/6537430?v=4?s=100" width="100px;" alt=""/><br /><sub><b>adamski.pro</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=akrystian" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/baislsl"><img src="https://avatars0.githubusercontent.com/u/17060584?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Shengli Bai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=baislsl" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/besok"><img src="https://avatars2.githubusercontent.com/u/29834592?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Boris</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=besok" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/dmitraver"><img src="https://avatars3.githubusercontent.com/u/1798156?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dmitry Avershin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dmitraver" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/fanofxiaofeng"><img src="https://avatars0.githubusercontent.com/u/3983683?v=4" width="100px;" alt=""/><br /><sub><b>靳阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fanofxiaofeng" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/hoangnam2261"><img src="https://avatars2.githubusercontent.com/u/31692990?v=4" width="100px;" alt=""/><br /><sub><b>hoangnam2261</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hoangnam2261" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/jarpit96"><img src="https://avatars2.githubusercontent.com/u/10098713?v=4" width="100px;" alt=""/><br /><sub><b>Arpit Jain</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jarpit96" title="Code">💻</a></td>
-    <td align="center"><a href="http://joningi.net"><img src="https://avatars2.githubusercontent.com/u/6115148?v=4" width="100px;" alt=""/><br /><sub><b>Jón Ingi Sveinbjörnsson</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=joningiwork" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/fanofxiaofeng"><img src="https://avatars0.githubusercontent.com/u/3983683?v=4?s=100" width="100px;" alt=""/><br /><sub><b>靳阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fanofxiaofeng" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/hoangnam2261"><img src="https://avatars2.githubusercontent.com/u/31692990?v=4?s=100" width="100px;" alt=""/><br /><sub><b>hoangnam2261</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hoangnam2261" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/jarpit96"><img src="https://avatars2.githubusercontent.com/u/10098713?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Arpit Jain</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jarpit96" title="Code">💻</a></td>
+    <td align="center"><a href="http://joningi.net"><img src="https://avatars2.githubusercontent.com/u/6115148?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jón Ingi Sveinbjörnsson</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=joningiwork" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/kirill-vlasov"><img src="https://avatars3.githubusercontent.com/u/16112495?v=4" width="100px;" alt=""/><br /><sub><b>Kirill Vlasov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kirill-vlasov" title="Code">💻</a></td>
-    <td align="center"><a href="http://mitchell-irvin.com"><img src="https://avatars0.githubusercontent.com/u/16233245?v=4" width="100px;" alt=""/><br /><sub><b>Mitchell Irvin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mitchellirvin" title="Code">💻</a></td>
-    <td align="center"><a href="https://ranjeet-floyd.github.io"><img src="https://avatars0.githubusercontent.com/u/1992972?v=4" width="100px;" alt=""/><br /><sub><b>Ranjeet</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ranjeet-floyd" title="Code">💻</a></td>
-    <td align="center"><a href="https://alwayswithme.github.io"><img src="https://avatars3.githubusercontent.com/u/3234786?v=4" width="100px;" alt=""/><br /><sub><b>PhoenixYip</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Alwayswithme" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/kirill-vlasov"><img src="https://avatars3.githubusercontent.com/u/16112495?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kirill Vlasov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kirill-vlasov" title="Code">💻</a></td>
+    <td align="center"><a href="http://mitchell-irvin.com"><img src="https://avatars0.githubusercontent.com/u/16233245?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mitchell Irvin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mitchellirvin" title="Code">💻</a></td>
+    <td align="center"><a href="https://ranjeet-floyd.github.io"><img src="https://avatars0.githubusercontent.com/u/1992972?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ranjeet</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ranjeet-floyd" title="Code">💻</a></td>
+    <td align="center"><a href="https://alwayswithme.github.io"><img src="https://avatars3.githubusercontent.com/u/3234786?v=4?s=100" width="100px;" alt=""/><br /><sub><b>PhoenixYip</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Alwayswithme" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/MSaifAsif"><img src="https://avatars1.githubusercontent.com/u/6280554?v=4" width="100px;" alt=""/><br /><sub><b>M Saif Asif</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=MSaifAsif" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/kanwarpreet25"><img src="https://avatars0.githubusercontent.com/u/39183641?v=4" width="100px;" alt=""/><br /><sub><b>kanwarpreet25</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kanwarpreet25" title="Code">💻</a></td>
-    <td align="center"><a href="http://leonmak.me"><img src="https://avatars3.githubusercontent.com/u/13071508?v=4" width="100px;" alt=""/><br /><sub><b>Leon Mak</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=leonmak" title="Code">💻</a></td>
-    <td align="center"><a href="http://www.wramdemark.se"><img src="https://avatars2.githubusercontent.com/u/7052193?v=4" width="100px;" alt=""/><br /><sub><b>Per Wramdemark</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=perwramdemark" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/MSaifAsif"><img src="https://avatars1.githubusercontent.com/u/6280554?v=4?s=100" width="100px;" alt=""/><br /><sub><b>M Saif Asif</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=MSaifAsif" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/kanwarpreet25"><img src="https://avatars0.githubusercontent.com/u/39183641?v=4?s=100" width="100px;" alt=""/><br /><sub><b>kanwarpreet25</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kanwarpreet25" title="Code">💻</a></td>
+    <td align="center"><a href="http://leonmak.me"><img src="https://avatars3.githubusercontent.com/u/13071508?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Leon Mak</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=leonmak" title="Code">💻</a></td>
+    <td align="center"><a href="http://www.wramdemark.se"><img src="https://avatars2.githubusercontent.com/u/7052193?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Per Wramdemark</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=perwramdemark" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/waisuan"><img src="https://avatars2.githubusercontent.com/u/10975700?v=4" width="100px;" alt=""/><br /><sub><b>Evan Sia Wai Suan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=waisuan" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/AnaghaSasikumar"><img src="https://avatars2.githubusercontent.com/u/42939261?v=4" width="100px;" alt=""/><br /><sub><b>AnaghaSasikumar</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=AnaghaSasikumar" title="Code">💻</a></td>
-    <td align="center"><a href="https://christofferh.com"><img src="https://avatars1.githubusercontent.com/u/767643?v=4" width="100px;" alt=""/><br /><sub><b>Christoffer Hamberg</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=christofferh" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/dgruntz"><img src="https://avatars0.githubusercontent.com/u/1516800?v=4" width="100px;" alt=""/><br /><sub><b>Dominik Gruntz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dgruntz" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/waisuan"><img src="https://avatars2.githubusercontent.com/u/10975700?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Evan Sia Wai Suan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=waisuan" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/AnaghaSasikumar"><img src="https://avatars2.githubusercontent.com/u/42939261?v=4?s=100" width="100px;" alt=""/><br /><sub><b>AnaghaSasikumar</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=AnaghaSasikumar" title="Code">💻</a></td>
+    <td align="center"><a href="https://christofferh.com"><img src="https://avatars1.githubusercontent.com/u/767643?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christoffer Hamberg</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=christofferh" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/dgruntz"><img src="https://avatars0.githubusercontent.com/u/1516800?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dominik Gruntz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dgruntz" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://bitbucket.org/hannespernpeintner/"><img src="https://avatars3.githubusercontent.com/u/1679437?v=4" width="100px;" alt=""/><br /><sub><b>Hannes</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hannespernpeintner" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/leogtzr"><img src="https://avatars0.githubusercontent.com/u/1211969?v=4" width="100px;" alt=""/><br /><sub><b>Leo Gutiérrez Ramírez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=leogtzr" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/npczwh"><img src="https://avatars0.githubusercontent.com/u/14066422?v=4" width="100px;" alt=""/><br /><sub><b>Zhang WH</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=npczwh" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/oconnelc"><img src="https://avatars0.githubusercontent.com/u/1112973?v=4" width="100px;" alt=""/><br /><sub><b>Christopher O'Connell</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=oconnelc" title="Code">💻</a></td>
+    <td align="center"><a href="https://bitbucket.org/hannespernpeintner/"><img src="https://avatars3.githubusercontent.com/u/1679437?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Hannes</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hannespernpeintner" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/leogtzr"><img src="https://avatars0.githubusercontent.com/u/1211969?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Leo Gutiérrez Ramírez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=leogtzr" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/npczwh"><img src="https://avatars0.githubusercontent.com/u/14066422?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Zhang WH</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=npczwh" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/oconnelc"><img src="https://avatars0.githubusercontent.com/u/1112973?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christopher O'Connell</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=oconnelc" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/giorgosmav21"><img src="https://avatars2.githubusercontent.com/u/22855493?v=4" width="100px;" alt=""/><br /><sub><b>George Mavroeidis</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=giorgosmav21" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/hbothra15"><img src="https://avatars1.githubusercontent.com/u/7418012?v=4" width="100px;" alt=""/><br /><sub><b>Hemant Bothra</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hbothra15" title="Code">💻</a> <a href="#design-hbothra15" title="Design">🎨</a></td>
-    <td align="center"><a href="https://www.kevinpeters.net/about/"><img src="https://avatars1.githubusercontent.com/u/12736734?v=4" width="100px;" alt=""/><br /><sub><b>Kevin Peters</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=igeligel" title="Code">💻</a></td>
-    <td align="center"><a href="https://llorllale.github.io/"><img src="https://avatars1.githubusercontent.com/u/2019896?v=4" width="100px;" alt=""/><br /><sub><b>George Aristy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=llorllale" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/giorgosmav21"><img src="https://avatars2.githubusercontent.com/u/22855493?v=4?s=100" width="100px;" alt=""/><br /><sub><b>George Mavroeidis</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=giorgosmav21" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/hbothra15"><img src="https://avatars1.githubusercontent.com/u/7418012?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Hemant Bothra</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hbothra15" title="Code">💻</a> <a href="#design-hbothra15" title="Design">🎨</a></td>
+    <td align="center"><a href="https://www.kevinpeters.net/about/"><img src="https://avatars1.githubusercontent.com/u/12736734?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kevin Peters</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=igeligel" title="Code">💻</a></td>
+    <td align="center"><a href="https://llorllale.github.io/"><img src="https://avatars1.githubusercontent.com/u/2019896?v=4?s=100" width="100px;" alt=""/><br /><sub><b>George Aristy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=llorllale" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/mookkiah"><img src="https://avatars1.githubusercontent.com/u/8975264?v=4" width="100px;" alt=""/><br /><sub><b>Mahendran Mookkiah</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mookkiah" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/Azureyjt"><img src="https://avatars2.githubusercontent.com/u/18476317?v=4" width="100px;" alt=""/><br /><sub><b>Azureyjt</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Azureyjt" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/vehpsr"><img src="https://avatars2.githubusercontent.com/u/3133265?v=4" width="100px;" alt=""/><br /><sub><b>gans</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vehpsr" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/ThatGuyWithTheHat"><img src="https://avatars0.githubusercontent.com/u/24470582?v=4" width="100px;" alt=""/><br /><sub><b>Matt</b></sub></a><br /><a href="#content-ThatGuyWithTheHat" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/mookkiah"><img src="https://avatars1.githubusercontent.com/u/8975264?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mahendran Mookkiah</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mookkiah" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Azureyjt"><img src="https://avatars2.githubusercontent.com/u/18476317?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Azureyjt</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Azureyjt" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/vehpsr"><img src="https://avatars2.githubusercontent.com/u/3133265?v=4?s=100" width="100px;" alt=""/><br /><sub><b>gans</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vehpsr" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ThatGuyWithTheHat"><img src="https://avatars0.githubusercontent.com/u/24470582?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Matt</b></sub></a><br /><a href="#content-ThatGuyWithTheHat" title="Content">🖋</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://www.linkedin.com/in/gopinathlangote/"><img src="https://avatars2.githubusercontent.com/u/10210778?v=4" width="100px;" alt=""/><br /><sub><b>Gopinath Langote</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gopinath-langote" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/hoswey"><img src="https://avatars3.githubusercontent.com/u/3689445?v=4" width="100px;" alt=""/><br /><sub><b>Hoswey</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hoswey" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/amit2103"><img src="https://avatars3.githubusercontent.com/u/7566692?v=4" width="100px;" alt=""/><br /><sub><b>Amit Pandey</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amit2103" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/gwildor28"><img src="https://avatars0.githubusercontent.com/u/16000365?v=4" width="100px;" alt=""/><br /><sub><b>gwildor28</b></sub></a><br /><a href="#content-gwildor28" title="Content">🖋</a></td>
+    <td align="center"><a href="https://www.linkedin.com/in/gopinathlangote/"><img src="https://avatars2.githubusercontent.com/u/10210778?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Gopinath Langote</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gopinath-langote" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/hoswey"><img src="https://avatars3.githubusercontent.com/u/3689445?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Hoswey</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hoswey" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/amit2103"><img src="https://avatars3.githubusercontent.com/u/7566692?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Amit Pandey</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amit2103" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/gwildor28"><img src="https://avatars0.githubusercontent.com/u/16000365?v=4?s=100" width="100px;" alt=""/><br /><sub><b>gwildor28</b></sub></a><br /><a href="#content-gwildor28" title="Content">🖋</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://t.me/paul_docker"><img src="https://avatars1.githubusercontent.com/u/2404785?v=4" width="100px;" alt=""/><br /><sub><b>田浩</b></sub></a><br /><a href="#content-llitfkitfk" title="Content">🖋</a></td>
-    <td align="center"><a href="https://twitter.com/StPitsios"><img src="https://avatars1.githubusercontent.com/u/6773603?v=4" width="100px;" alt=""/><br /><sub><b>Stamatis Pitsios</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=pitsios-s" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/qza"><img src="https://avatars3.githubusercontent.com/u/233149?v=4" width="100px;" alt=""/><br /><sub><b>qza</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qza" title="Code">💻</a></td>
-    <td align="center"><a href="http://tschis.github.io"><img src="https://avatars1.githubusercontent.com/u/20662669?v=4" width="100px;" alt=""/><br /><sub><b>Rodolfo Forte</b></sub></a><br /><a href="#content-Tschis" title="Content">🖋</a></td>
+    <td align="center"><a href="https://t.me/paul_docker"><img src="https://avatars1.githubusercontent.com/u/2404785?v=4?s=100" width="100px;" alt=""/><br /><sub><b>田浩</b></sub></a><br /><a href="#content-llitfkitfk" title="Content">🖋</a></td>
+    <td align="center"><a href="https://twitter.com/StPitsios"><img src="https://avatars1.githubusercontent.com/u/6773603?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Stamatis Pitsios</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=pitsios-s" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/qza"><img src="https://avatars3.githubusercontent.com/u/233149?v=4?s=100" width="100px;" alt=""/><br /><sub><b>qza</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qza" title="Code">💻</a></td>
+    <td align="center"><a href="http://tschis.github.io"><img src="https://avatars1.githubusercontent.com/u/20662669?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rodolfo Forte</b></sub></a><br /><a href="#content-Tschis" title="Content">🖋</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/ankurkaushal"><img src="https://avatars2.githubusercontent.com/u/2236616?v=4" width="100px;" alt=""/><br /><sub><b>Ankur Kaushal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ankurkaushal" title="Code">💻</a></td>
-    <td align="center"><a href="https://www.linkedin.com/in/ovidijus-okinskas/"><img src="https://avatars0.githubusercontent.com/u/20372387?v=4" width="100px;" alt=""/><br /><sub><b>Ovidijus Okinskas</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=okinskas" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/robertt240"><img src="https://avatars1.githubusercontent.com/u/9137432?v=4" width="100px;" alt=""/><br /><sub><b>Robert Kasperczyk</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=robertt240" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/trautonen"><img src="https://avatars3.githubusercontent.com/u/1641063?v=4" width="100px;" alt=""/><br /><sub><b>Tapio Rautonen</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=trautonen" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ankurkaushal"><img src="https://avatars2.githubusercontent.com/u/2236616?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ankur Kaushal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ankurkaushal" title="Code">💻</a></td>
+    <td align="center"><a href="https://www.linkedin.com/in/ovidijus-okinskas/"><img src="https://avatars0.githubusercontent.com/u/20372387?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ovidijus Okinskas</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=okinskas" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/robertt240"><img src="https://avatars1.githubusercontent.com/u/9137432?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Robert Kasperczyk</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=robertt240" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/trautonen"><img src="https://avatars3.githubusercontent.com/u/1641063?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Tapio Rautonen</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=trautonen" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="http://vk.com/yuri.orlov"><img src="https://avatars0.githubusercontent.com/u/1595733?v=4" width="100px;" alt=""/><br /><sub><b>Yuri Orlov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yorlov" title="Code">💻</a></td>
-    <td align="center"><a href="https://www.linkedin.com/in/varunu28/"><img src="https://avatars0.githubusercontent.com/u/7676016?v=4" width="100px;" alt=""/><br /><sub><b>Varun Upadhyay</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=varunu28" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/PalAditya"><img src="https://avatars2.githubusercontent.com/u/25523604?v=4" width="100px;" alt=""/><br /><sub><b>Aditya Pal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=PalAditya" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/grzesiekkedzior"><img src="https://avatars3.githubusercontent.com/u/23739158?v=4" width="100px;" alt=""/><br /><sub><b>grzesiekkedzior</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=grzesiekkedzior" title="Code">💻</a></td>
+    <td align="center"><a href="http://vk.com/yuri.orlov"><img src="https://avatars0.githubusercontent.com/u/1595733?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Yuri Orlov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yorlov" title="Code">💻</a></td>
+    <td align="center"><a href="https://www.linkedin.com/in/varunu28/"><img src="https://avatars0.githubusercontent.com/u/7676016?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Varun Upadhyay</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=varunu28" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/PalAditya"><img src="https://avatars2.githubusercontent.com/u/25523604?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Aditya Pal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=PalAditya" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/grzesiekkedzior"><img src="https://avatars3.githubusercontent.com/u/23739158?v=4?s=100" width="100px;" alt=""/><br /><sub><b>grzesiekkedzior</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=grzesiekkedzior" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Agrzesiekkedzior" title="Reviewed Pull Requests">👀</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/sivasubramanim"><img src="https://avatars2.githubusercontent.com/u/51107434?v=4" width="100px;" alt=""/><br /><sub><b>Sivasubramani M</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=sivasubramanim" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/d4gg4d"><img src="https://avatars2.githubusercontent.com/u/99457?v=4" width="100px;" alt=""/><br /><sub><b>Sami Airaksinen</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=d4gg4d" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/vertti"><img src="https://avatars0.githubusercontent.com/u/557751?v=4" width="100px;" alt=""/><br /><sub><b>Janne Sinivirta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vertti" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/Bobo1239"><img src="https://avatars1.githubusercontent.com/u/2302947?v=4" width="100px;" alt=""/><br /><sub><b>Boris-Chengbiao Zhou</b></sub></a><br /><a href="#content-Bobo1239" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/sivasubramanim"><img src="https://avatars2.githubusercontent.com/u/51107434?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sivasubramani M</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=sivasubramanim" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/d4gg4d"><img src="https://avatars2.githubusercontent.com/u/99457?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sami Airaksinen</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=d4gg4d" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/vertti"><img src="https://avatars0.githubusercontent.com/u/557751?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Janne Sinivirta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vertti" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Bobo1239"><img src="https://avatars1.githubusercontent.com/u/2302947?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Boris-Chengbiao Zhou</b></sub></a><br /><a href="#content-Bobo1239" title="Content">🖋</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://jahhein.github.io"><img src="https://avatars2.githubusercontent.com/u/10779515?v=4" width="100px;" alt=""/><br /><sub><b>Jacob Hein</b></sub></a><br /><a href="#content-Jahhein" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/iamrichardjones"><img src="https://avatars3.githubusercontent.com/u/14842151?v=4" width="100px;" alt=""/><br /><sub><b>Richard Jones</b></sub></a><br /><a href="#content-iamrichardjones" title="Content">🖋</a></td>
-    <td align="center"><a href="https://rachelcarmena.github.io"><img src="https://avatars0.githubusercontent.com/u/22792183?v=4" width="100px;" alt=""/><br /><sub><b>Rachel M. Carmena</b></sub></a><br /><a href="#content-rachelcarmena" title="Content">🖋</a></td>
-    <td align="center"><a href="https://zd-zero.github.io"><img src="https://avatars0.githubusercontent.com/u/21978370?v=4" width="100px;" alt=""/><br /><sub><b>Zaerald Denze Lungos</b></sub></a><br /><a href="#content-zd-zero" title="Content">🖋</a></td>
+    <td align="center"><a href="https://jahhein.github.io"><img src="https://avatars2.githubusercontent.com/u/10779515?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jacob Hein</b></sub></a><br /><a href="#content-Jahhein" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/iamrichardjones"><img src="https://avatars3.githubusercontent.com/u/14842151?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Richard Jones</b></sub></a><br /><a href="#content-iamrichardjones" title="Content">🖋</a></td>
+    <td align="center"><a href="https://rachelcarmena.github.io"><img src="https://avatars0.githubusercontent.com/u/22792183?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rachel M. Carmena</b></sub></a><br /><a href="#content-rachelcarmena" title="Content">🖋</a></td>
+    <td align="center"><a href="https://zd-zero.github.io"><img src="https://avatars0.githubusercontent.com/u/21978370?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Zaerald Denze Lungos</b></sub></a><br /><a href="#content-zd-zero" title="Content">🖋</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://webpro.nl"><img src="https://avatars1.githubusercontent.com/u/456426?v=4" width="100px;" alt=""/><br /><sub><b>Lars Kappert</b></sub></a><br /><a href="#content-webpro" title="Content">🖋</a></td>
-    <td align="center"><a href="https://xiaod.info"><img src="https://avatars2.githubusercontent.com/u/21277644?v=4" width="100px;" alt=""/><br /><sub><b>Mike Liu</b></sub></a><br /><a href="#translation-xiaod-dev" title="Translation">🌍</a></td>
-    <td align="center"><a href="https://github.com/charlesfinley"><img src="https://avatars1.githubusercontent.com/u/6307904?v=4" width="100px;" alt=""/><br /><sub><b>Matt Dolan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=charlesfinley" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Acharlesfinley" title="Reviewed Pull Requests">👀</a></td>
-    <td align="center"><a href="https://github.com/MananS77"><img src="https://avatars3.githubusercontent.com/u/21033516?v=4" width="100px;" alt=""/><br /><sub><b>Manan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AMananS77" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://webpro.nl"><img src="https://avatars1.githubusercontent.com/u/456426?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Lars Kappert</b></sub></a><br /><a href="#content-webpro" title="Content">🖋</a></td>
+    <td align="center"><a href="https://xiaod.info"><img src="https://avatars2.githubusercontent.com/u/21277644?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mike Liu</b></sub></a><br /><a href="#translation-xiaod-dev" title="Translation">🌍</a></td>
+    <td align="center"><a href="https://github.com/charlesfinley"><img src="https://avatars1.githubusercontent.com/u/6307904?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Matt Dolan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=charlesfinley" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Acharlesfinley" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://github.com/MananS77"><img src="https://avatars3.githubusercontent.com/u/21033516?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Manan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AMananS77" title="Reviewed Pull Requests">👀</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/nishant"><img src="https://avatars2.githubusercontent.com/u/15331971?v=4" width="100px;" alt=""/><br /><sub><b>Nishant Arora</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nishant" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/raja-peeyush-kumar-singh"><img src="https://avatars0.githubusercontent.com/u/5496024?v=4" width="100px;" alt=""/><br /><sub><b>Peeyush</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=raja-peeyush-kumar-singh" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/ravening"><img src="https://avatars1.githubusercontent.com/u/10645273?v=4" width="100px;" alt=""/><br /><sub><b>Rakesh</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ravening" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/vINCENT8888801"><img src="https://avatars0.githubusercontent.com/u/8037883?v=4" width="100px;" alt=""/><br /><sub><b>Wei Seng</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vINCENT8888801" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/nishant"><img src="https://avatars2.githubusercontent.com/u/15331971?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Nishant Arora</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nishant" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/raja-peeyush-kumar-singh"><img src="https://avatars0.githubusercontent.com/u/5496024?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Peeyush</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=raja-peeyush-kumar-singh" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ravening"><img src="https://avatars1.githubusercontent.com/u/10645273?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rakesh</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ravening" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aravening" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://github.com/vINCENT8888801"><img src="https://avatars0.githubusercontent.com/u/8037883?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Wei Seng</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vINCENT8888801" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://www.linkedin.com/in/ashish-trivedi-218379135/"><img src="https://avatars3.githubusercontent.com/u/23194128?v=4" width="100px;" alt=""/><br /><sub><b>Ashish Trivedi</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ashishtrivedi16" title="Code">💻</a></td>
-    <td align="center"><a href="https://rayyounghong.com"><img src="https://avatars1.githubusercontent.com/u/41055099?v=4" width="100px;" alt=""/><br /><sub><b>洪月阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=RayYH" title="Code">💻</a></td>
-    <td align="center"><a href="https://xdvrx1.github.io/"><img src="https://avatars0.githubusercontent.com/u/47092464?v=4" width="100px;" alt=""/><br /><sub><b>xdvrx1</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Axdvrx1" title="Reviewed Pull Requests">👀</a> <a href="#ideas-xdvrx1" title="Ideas, Planning, & Feedback">🤔</a></td>
-    <td align="center"><a href="http://subho.xyz"><img src="https://avatars0.githubusercontent.com/u/13291222?v=4" width="100px;" alt=""/><br /><sub><b>Subhrodip Mohanta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ohbus" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aohbus" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://www.linkedin.com/in/ashish-trivedi-218379135/"><img src="https://avatars3.githubusercontent.com/u/23194128?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ashish Trivedi</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ashishtrivedi16" title="Code">💻</a></td>
+    <td align="center"><a href="https://rayyounghong.com"><img src="https://avatars1.githubusercontent.com/u/41055099?v=4?s=100" width="100px;" alt=""/><br /><sub><b>洪月阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=RayYH" title="Code">💻</a></td>
+    <td align="center"><a href="https://xdvrx1.github.io/"><img src="https://avatars0.githubusercontent.com/u/47092464?v=4?s=100" width="100px;" alt=""/><br /><sub><b>xdvrx1</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Axdvrx1" title="Reviewed Pull Requests">👀</a> <a href="#ideas-xdvrx1" title="Ideas, Planning, & Feedback">🤔</a></td>
+    <td align="center"><a href="http://subho.xyz"><img src="https://avatars0.githubusercontent.com/u/13291222?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Subhrodip Mohanta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ohbus" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aohbus" title="Reviewed Pull Requests">👀</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/nahteb"><img src="https://avatars3.githubusercontent.com/u/13121570?v=4" width="100px;" alt=""/><br /><sub><b>Bethan Palmer</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nahteb" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/ToxicDreamz"><img src="https://avatars0.githubusercontent.com/u/45225562?v=4" width="100px;" alt=""/><br /><sub><b>Toxic Dreamz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ToxicDreamz" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/nahteb"><img src="https://avatars3.githubusercontent.com/u/13121570?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Bethan Palmer</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nahteb" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ToxicDreamz"><img src="https://avatars0.githubusercontent.com/u/45225562?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Toxic Dreamz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ToxicDreamz" title="Code">💻</a></td>
+    <td align="center"><a href="http://www.edycutjong.com"><img src="https://avatars1.githubusercontent.com/u/1098102?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Edy Cu Tjong</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=edycutjong" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/mkrzywanski"><img src="https://avatars0.githubusercontent.com/u/15279585?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Michał Krzywański</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mkrzywanski" title="Code">💻</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://www.stefan-birkner.de"><img src="https://avatars1.githubusercontent.com/u/711349?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Stefan Birkner</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=stefanbirkner" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/fedorskvorcov"><img src="https://avatars3.githubusercontent.com/u/43882212?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Fedor Skvorcov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fedorskvorcov" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/samilAyoub"><img src="https://avatars0.githubusercontent.com/u/61546990?v=4?s=100" width="100px;" alt=""/><br /><sub><b>samilAyoub</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=samilAyoub" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/vdlald"><img src="https://avatars0.githubusercontent.com/u/29997701?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Vladislav Golubinov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vdlald" title="Code">💻</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://github.com/swarajsaaj"><img src="https://avatars2.githubusercontent.com/u/6285049?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Swaraj</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=swarajsaaj" title="Code">💻</a></td>
+    <td align="center"><a href="http://christophflick.de"><img src="https://avatars0.githubusercontent.com/u/4465376?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christoph Flick</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ChFlick" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/Ascenio"><img src="https://avatars1.githubusercontent.com/u/7662016?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ascênio</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AAscenio" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://www.linkedin.com/in/domenico-sibilio/"><img src="https://avatars2.githubusercontent.com/u/24280982?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Domenico Sibilio</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dsibilio" title="Documentation">📖</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://github.com/akashchandwani"><img src="https://avatars2.githubusercontent.com/u/3483277?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Akash Chandwani</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aakashchandwani" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="http://www.linkedin.com/in/manannikov"><img src="https://avatars2.githubusercontent.com/u/7019769?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Pavlo Manannikov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=manannikov" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/eimanip"><img src="https://avatars0.githubusercontent.com/u/20307301?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Eiman</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=eimanip" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/OrangePants-R"><img src="https://avatars0.githubusercontent.com/u/42976136?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rocky</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=OrangePants-R" title="Documentation">📖</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://ibrahimalii.github.io/"><img src="https://avatars2.githubusercontent.com/u/21141301?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ibrahim ali abdelghany</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AibrahimAlii" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://github.com/gkulkarni2020"><img src="https://avatars3.githubusercontent.com/u/5161548?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Girish Kulkarni</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gkulkarni2020" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/omk13"><img src="https://avatars0.githubusercontent.com/u/59054172?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Omar Karazoun</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=omk13" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/jeff303"><img src="https://avatars0.githubusercontent.com/u/3521562?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jeff Evans</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jeff303" title="Code">💻</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://viveksb007.github.io"><img src="https://avatars1.githubusercontent.com/u/12713808?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Vivek Singh</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=viveksb007" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/siavashsoleymani"><img src="https://avatars2.githubusercontent.com/u/18074419?v=4?s=100" width="100px;" alt=""/><br /><sub><b>siavash</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=siavashsoleymani" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ruchpeanuts"><img src="https://avatars0.githubusercontent.com/u/29301900?v=4?s=100" width="100px;" alt=""/><br /><sub><b>ruchpeanuts</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ruchpeanuts" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/warp125"><img src="https://avatars1.githubusercontent.com/u/48073115?v=4?s=100" width="100px;" alt=""/><br /><sub><b>warp125</b></sub></a><br /><a href="#translation-warp125" title="Translation">🌍</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="http://libkhadir.fr"><img src="https://avatars1.githubusercontent.com/u/45130488?v=4?s=100" width="100px;" alt=""/><br /><sub><b>KHADIR Tayeb</b></sub></a><br /><a href="#translation-tkhadir" title="Translation">🌍</a></td>
+    <td align="center"><a href="https://github.com/ignite1771"><img src="https://avatars2.githubusercontent.com/u/59446563?v=4?s=100" width="100px;" alt=""/><br /><sub><b>ignite1771</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ignite1771" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/demirhalil"><img src="https://avatars1.githubusercontent.com/u/22895118?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Halil Demir</b></sub></a><br /><a href="#translation-demirhalil" title="Translation">🌍</a></td>
   </tr>
 </table>
 
-<!-- markdownlint-enable -->
+<!-- markdownlint-restore -->
 <!-- prettier-ignore-end -->
+
 <!-- ALL-CONTRIBUTORS-LIST:END -->

abstract-document/pom.xml

@@ -21,7 +21,7 @@
 	<parent>
 		<artifactId>java-design-patterns</artifactId>
 		<groupId>com.iluwatar</groupId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>abstract-document</artifactId>
 	<dependencies>

abstract-factory/pom.xml

@@ -22,7 +22,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>abstract-factory</artifactId>
 	<dependencies>

abstract-factory/src/main/java/com/iluwatar/abstractfactory/App.java

@@ -23,7 +23,6 @@
 
 package com.iluwatar.abstractfactory;
 
-import com.iluwatar.abstractfactory.App.FactoryMaker.KingdomType;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -41,84 +40,14 @@ import org.slf4j.LoggerFactory;
  * and its implementations ( {@link ElfKingdomFactory}, {@link OrcKingdomFactory}). The example uses
  * both concrete implementations to create a king, a castle and an army.
  */
-public class App {
+public class App implements Runnable {
 
-  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
+  private static Logger log = LoggerFactory.getLogger(App.class);
 
-  private King king;
-  private Castle castle;
-  private Army army;
+  private final Kingdom kingdom = new Kingdom();
 
-  /**
-   * Creates kingdom.
-   */
-  public void createKingdom(final KingdomFactory factory) {
-    setKing(factory.createKing());
-    setCastle(factory.createCastle());
-    setArmy(factory.createArmy());
-  }
-
-  King getKing(final KingdomFactory factory) {
-    return factory.createKing();
-  }
-
-  public King getKing() {
-    return king;
-  }
-
-  private void setKing(final King king) {
-    this.king = king;
-  }
-
-  Castle getCastle(final KingdomFactory factory) {
-    return factory.createCastle();
-  }
-
-  public Castle getCastle() {
-    return castle;
-  }
-
-  private void setCastle(final Castle castle) {
-    this.castle = castle;
-  }
-
-  Army getArmy(final KingdomFactory factory) {
-    return factory.createArmy();
-  }
-
-  public Army getArmy() {
-    return army;
-  }
-
-  private void setArmy(final Army army) {
-    this.army = army;
-  }
-
-  /**
-   * The factory of kingdom factories.
-   */
-  public static class FactoryMaker {
-
-    /**
-     * Enumeration for the different types of Kingdoms.
-     */
-    public enum KingdomType {
-      ELF, ORC
-    }
-
-    /**
-     * The factory method to create KingdomFactory concrete objects.
-     */
-    public static KingdomFactory makeFactory(KingdomType type) {
-      switch (type) {
-        case ELF:
-          return new ElfKingdomFactory();
-        case ORC:
-          return new OrcKingdomFactory();
-        default:
-          throw new IllegalArgumentException("KingdomType not supported.");
-      }
-    }
+  public Kingdom getKingdom() {
+    return kingdom;
   }
 
   /**
@@ -127,19 +56,33 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-
     var app = new App();
+    app.run();
+  }
 
-    LOGGER.info("Elf Kingdom");
-    app.createKingdom(FactoryMaker.makeFactory(KingdomType.ELF));
-    LOGGER.info(app.getArmy().getDescription());
-    LOGGER.info(app.getCastle().getDescription());
-    LOGGER.info(app.getKing().getDescription());
+  @Override
+  public void run() {
+    log.info("Elf Kingdom");
+    createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+    log.info(kingdom.getArmy().getDescription());
+    log.info(kingdom.getCastle().getDescription());
+    log.info(kingdom.getKing().getDescription());
 
-    LOGGER.info("Orc Kingdom");
-    app.createKingdom(FactoryMaker.makeFactory(KingdomType.ORC));
-    LOGGER.info(app.getArmy().getDescription());
-    LOGGER.info(app.getCastle().getDescription());
-    LOGGER.info(app.getKing().getDescription());
+    log.info("Orc Kingdom");
+    createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+    log.info(kingdom.getArmy().getDescription());
+    log.info(kingdom.getCastle().getDescription());
+    log.info(kingdom.getKing().getDescription());
+  }
+
+  /**
+   * Creates kingdom.
+   * @param kingdomType type of Kingdom
+   */
+  public void createKingdom(final Kingdom.FactoryMaker.KingdomType kingdomType) {
+    final KingdomFactory kingdomFactory = Kingdom.FactoryMaker.makeFactory(kingdomType);
+    kingdom.setKing(kingdomFactory.createKing());
+    kingdom.setCastle(kingdomFactory.createCastle());
+    kingdom.setArmy(kingdomFactory.createArmy());
   }
 }

abstract-factory/src/main/java/com/iluwatar/abstractfactory/Kingdom.java

@@ -0,0 +1,82 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.abstractfactory;
+
+public class Kingdom {
+
+  private King king;
+  private Castle castle;
+  private Army army;
+
+  public King getKing() {
+    return king;
+  }
+
+  public Castle getCastle() {
+    return castle;
+  }
+
+  public Army getArmy() {
+    return army;
+  }
+
+  public void setKing(King king) {
+    this.king = king;
+  }
+
+  public void setCastle(Castle castle) {
+    this.castle = castle;
+  }
+
+  public void setArmy(Army army) {
+    this.army = army;
+  }
+
+  /**
+   * The factory of kingdom factories.
+   */
+  public static class FactoryMaker {
+
+    /**
+     * Enumeration for the different types of Kingdoms.
+     */
+    public enum KingdomType {
+      ELF, ORC
+    }
+
+    /**
+     * The factory method to create KingdomFactory concrete objects.
+     */
+    public static KingdomFactory makeFactory(KingdomType type) {
+      switch (type) {
+        case ELF:
+          return new ElfKingdomFactory();
+        case ORC:
+          return new OrcKingdomFactory();
+        default:
+          throw new IllegalArgumentException("KingdomType not supported.");
+      }
+    }
+  }
+}

abstract-factory/src/test/java/com/iluwatar/abstractfactory/AbstractFactoryTest.java

@@ -23,65 +23,71 @@
 
 package com.iluwatar.abstractfactory;
 
+import org.junit.jupiter.api.Test;
+
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
-import com.iluwatar.abstractfactory.App.FactoryMaker;
-import com.iluwatar.abstractfactory.App.FactoryMaker.KingdomType;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Test;
-
 /**
  * Test for abstract factory.
  */
 public class AbstractFactoryTest {
 
   private final App app = new App();
-  private KingdomFactory elfFactory;
-  private KingdomFactory orcFactory;
-
-  @BeforeEach
-  public void setUp() {
-    elfFactory = FactoryMaker.makeFactory(KingdomType.ELF);
-    orcFactory = FactoryMaker.makeFactory(KingdomType.ORC);
-  }
 
   @Test
   public void king() {
-    final var elfKing = app.getKing(elfFactory);
+    app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+    final var kingdom = app.getKingdom();
+
+    final var elfKing = kingdom.getKing();
     assertTrue(elfKing instanceof ElfKing);
     assertEquals(ElfKing.DESCRIPTION, elfKing.getDescription());
-    final var orcKing = app.getKing(orcFactory);
+
+    app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+    final var orcKing = kingdom.getKing();
     assertTrue(orcKing instanceof OrcKing);
     assertEquals(OrcKing.DESCRIPTION, orcKing.getDescription());
   }
 
   @Test
   public void castle() {
-    final var elfCastle = app.getCastle(elfFactory);
+    app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+    final var kingdom = app.getKingdom();
+
+    final var elfCastle = kingdom.getCastle();
     assertTrue(elfCastle instanceof ElfCastle);
     assertEquals(ElfCastle.DESCRIPTION, elfCastle.getDescription());
-    final var orcCastle = app.getCastle(orcFactory);
+
+    app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+    final var orcCastle = kingdom.getCastle();
     assertTrue(orcCastle instanceof OrcCastle);
     assertEquals(OrcCastle.DESCRIPTION, orcCastle.getDescription());
   }
 
   @Test
   public void army() {
-    final var elfArmy = app.getArmy(elfFactory);
+    app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+    final var kingdom = app.getKingdom();
+
+    final var elfArmy = kingdom.getArmy();
     assertTrue(elfArmy instanceof ElfArmy);
     assertEquals(ElfArmy.DESCRIPTION, elfArmy.getDescription());
-    final var orcArmy = app.getArmy(orcFactory);
+
+    app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+    final var orcArmy = kingdom.getArmy();
     assertTrue(orcArmy instanceof OrcArmy);
     assertEquals(OrcArmy.DESCRIPTION, orcArmy.getDescription());
   }
 
   @Test
   public void createElfKingdom() {
-    app.createKingdom(elfFactory);
-    final var king = app.getKing();
-    final var castle = app.getCastle();
-    final var army = app.getArmy();
+    app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+    final var kingdom = app.getKingdom();
+
+    final var king = kingdom.getKing();
+    final var castle = kingdom.getCastle();
+    final var army = kingdom.getArmy();
     assertTrue(king instanceof ElfKing);
     assertEquals(ElfKing.DESCRIPTION, king.getDescription());
     assertTrue(castle instanceof ElfCastle);
@@ -92,10 +98,12 @@ public class AbstractFactoryTest {
 
   @Test
   public void createOrcKingdom() {
-    app.createKingdom(orcFactory);
-    final var king = app.getKing();
-    final var castle = app.getCastle();
-    final var army = app.getArmy();
+    app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+    final var kingdom = app.getKingdom();
+
+    final var king = kingdom.getKing();
+    final var castle = kingdom.getCastle();
+    final var army = kingdom.getArmy();
     assertTrue(king instanceof OrcKing);
     assertEquals(OrcKing.DESCRIPTION, king.getDescription());
     assertTrue(castle instanceof OrcCastle);

acyclic-visitor/pom.xml

@@ -21,7 +21,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 
 	<artifactId>acyclic-visitor</artifactId>

adapter/pom.xml

@@ -22,7 +22,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>adapter</artifactId>
 	<dependencies>

aggregator-microservices/aggregator-service/pom.xml

@@ -20,7 +20,7 @@
 	<parent>
 		<artifactId>aggregator-microservices</artifactId>
 		<groupId>com.iluwatar</groupId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<modelVersion>4.0.0</modelVersion>
 	<artifactId>aggregator-service</artifactId>

aggregator-microservices/information-microservice/pom.xml

@@ -20,7 +20,7 @@
 	<parent>
 		<artifactId>aggregator-microservices</artifactId>
 		<groupId>com.iluwatar</groupId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<modelVersion>4.0.0</modelVersion>
 

aggregator-microservices/inventory-microservice/pom.xml

@@ -20,7 +20,7 @@
 	<parent>
 		<artifactId>aggregator-microservices</artifactId>
 		<groupId>com.iluwatar</groupId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<modelVersion>4.0.0</modelVersion>
 	<artifactId>inventory-microservice</artifactId>

aggregator-microservices/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.23.0-SNAPSHOT</version>
+        <version>1.24.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
     <artifactId>aggregator-microservices</artifactId>

ambassador/pom.xml

@@ -20,7 +20,7 @@
 	<parent>
 		<artifactId>java-design-patterns</artifactId>
 		<groupId>com.iluwatar</groupId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<modelVersion>4.0.0</modelVersion>
 	<artifactId>ambassador</artifactId>

api-gateway/api-gateway-service/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>api-gateway</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>api-gateway-service</artifactId>

api-gateway/image-microservice/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>api-gateway</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>image-microservice</artifactId>

api-gateway/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>api-gateway</artifactId>

api-gateway/price-microservice/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>api-gateway</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
 
   <modelVersion>4.0.0</modelVersion>

arrange-act-assert/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
 

async-method-invocation/pom.xml

@@ -22,7 +22,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>async-method-invocation</artifactId>
 	<dependencies>

balking/pom.xml

@@ -20,7 +20,7 @@
 	<parent>
 		<artifactId>java-design-patterns</artifactId>
 		<groupId>com.iluwatar</groupId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<modelVersion>4.0.0</modelVersion>
 

bridge/README.md

@@ -9,20 +9,26 @@ tags:
 ---
 
 ## Also known as
+
 Handle/Body
 
 ## Intent
+
 Decouple an abstraction from its implementation so that the two can vary independently.
 
 ## Explanation
 
 Real world example
 
-> Consider you have a weapon with different enchantments and you are supposed to allow mixing different weapons with different enchantments. What would you do? Create multiple copies of each of the weapons for each of the enchantments or would you just create separate enchantment and set it for the weapon as needed? Bridge pattern allows you to do the second.
+> Consider you have a weapon with different enchantments, and you are supposed to allow mixing 
+> different weapons with different enchantments. What would you do? Create multiple copies of each 
+> of the weapons for each of the enchantments or would you just create separate enchantment and set 
+> it for the weapon as needed? Bridge pattern allows you to do the second.
 
 In Plain Words
 
-> Bridge pattern is about preferring composition over inheritance. Implementation details are pushed from a hierarchy to another object with a separate hierarchy.
+> Bridge pattern is about preferring composition over inheritance. Implementation details are pushed 
+> from a hierarchy to another object with a separate hierarchy.
 
 Wikipedia says
 
@@ -30,7 +36,7 @@ Wikipedia says
 
 **Programmatic Example**
 
-Translating our weapon example from above. Here we have the `Weapon` hierarchy
+Translating our weapon example from above. Here we have the `Weapon` hierarchy:
 
 ```java
 public interface Weapon {
@@ -105,7 +111,7 @@ public class Hammer implements Weapon {
 }
 ```
 
-And the separate enchantment hierarchy
+Here's the separate enchantment hierarchy:
 
 ```java
 public interface Enchantment {
@@ -151,7 +157,7 @@ public class SoulEatingEnchantment implements Enchantment {
 }
 ```
 
-And both the hierarchies in action
+Here are both hierarchies in action:
 
 ```java
 var enchantedSword = new Sword(new SoulEatingEnchantment());
@@ -178,18 +184,21 @@ hammer.unwield();
 ```
 
 ## Class diagram
+
 ![alt text](./etc/bridge.urm.png "Bridge class diagram")
 
 ## Applicability
+
 Use the Bridge pattern when
 
-* you want to avoid a permanent binding between an abstraction and its implementation. This might be the case, for example, when the implementation must be selected or switched at run-time.
-* both the abstractions and their implementations should be extensible by subclassing. In this case, the Bridge pattern lets you combine the different abstractions and implementations and extend them independently
-* changes in the implementation of an abstraction should have no impact on clients; that is, their code should not have to be recompiled.
-* you have a proliferation of classes. Such a class hierarchy indicates the need for splitting an object into two parts. Rumbaugh uses the term "nested generalizations" to refer to such class hierarchies
-* you want to share an implementation among multiple objects (perhaps using reference counting), and this fact should be hidden from the client. A simple example is Coplien's String class, in which multiple objects can share the same string representation.
+* You want to avoid a permanent binding between an abstraction and its implementation. This might be the case, for example, when the implementation must be selected or switched at run-time.
+* Both the abstractions and their implementations should be extensible by subclassing. In this case, the Bridge pattern lets you combine the different abstractions and implementations and extend them independently.
+* Changes in the implementation of an abstraction should have no impact on clients; that is, their code should not have to be recompiled.
+* You have a proliferation of classes. Such a class hierarchy indicates the need for splitting an object into two parts. Rumbaugh uses the term "nested generalizations" to refer to such class hierarchies.
+* You want to share an implementation among multiple objects (perhaps using reference counting), and this fact should be hidden from the client. A simple example is Coplien's String class, in which multiple objects can share the same string representation.
 
 ## Tutorial
+
 * [Bridge Pattern Tutorial](https://www.journaldev.com/1491/bridge-design-pattern-java)
 
 ## Credits

bridge/pom.xml

@@ -22,7 +22,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>bridge</artifactId>
 	<dependencies>

builder/README.md

@@ -9,36 +9,47 @@ tags:
 ---
 
 ## Intent
-Separate the construction of a complex object from its
-representation so that the same construction process can create different
-representations.
+
+Separate the construction of a complex object from its representation so that the same construction 
+process can create different representations.
 
 ## Explanation
 
 Real world example
 
-> Imagine a character generator for a role playing game. The easiest option is to let computer create the character for you. But if you want to select the character details like profession, gender, hair color etc. the character generation becomes a step-by-step process that completes when all the selections are ready.
+> Imagine a character generator for a role-playing game. The easiest option is to let the computer 
+> create the character for you. If you want to manually select the character details like 
+> profession, gender, hair color etc. the character generation becomes a step-by-step process that 
+> completes when all the selections are ready.
 
 In plain words
 
-> Allows you to create different flavors of an object while avoiding constructor pollution. Useful when there could be several flavors of an object. Or when there are a lot of steps involved in creation of an object.
+> Allows you to create different flavors of an object while avoiding constructor pollution. Useful 
+> when there could be several flavors of an object. Or when there are a lot of steps involved in 
+> creation of an object.
 
 Wikipedia says
 
-> The builder pattern is an object creation software design pattern with the intentions of finding a solution to the telescoping constructor anti-pattern.
+> The builder pattern is an object creation software design pattern with the intentions of finding 
+> a solution to the telescoping constructor anti-pattern.
 
-Having said that let me add a bit about what telescoping constructor anti-pattern is. At one point or the other we have all seen a constructor like below:
+Having said that let me add a bit about what telescoping constructor anti-pattern is. At one point 
+or the other, we have all seen a constructor like below:
 
 ```java
 public Hero(Profession profession, String name, HairType hairType, HairColor hairColor, Armor armor, Weapon weapon) {
 }
 ```
 
-As you can see the number of constructor parameters can quickly get out of hand and it might become difficult to understand the arrangement of parameters. Plus this parameter list could keep on growing if you would want to add more options in future. This is called telescoping constructor anti-pattern.
+As you can see the number of constructor parameters can quickly get out of hand, and it may become 
+difficult to understand the arrangement of parameters. Plus this parameter list could keep on 
+growing if you would want to add more options in the future. This is called telescoping constructor 
+anti-pattern.
 
 **Programmatic Example**
 
-The sane alternative is to use the Builder pattern. First of all we have our hero that we want to create
+The sane alternative is to use the Builder pattern. First of all we have our hero that we want to 
+create:
 
 ```java
 public final class Hero {
@@ -60,7 +71,7 @@ public final class Hero {
 }
 ```
 
-And then we have the builder
+Then we have the builder:
 
 ```java
   public static class Builder {
@@ -105,20 +116,22 @@ And then we have the builder
   }
 ```
 
-And then it can be used as:
+Then it can be used as:
 
 ```java
 var mage = new Hero.Builder(Profession.MAGE, "Riobard").withHairColor(HairColor.BLACK).withWeapon(Weapon.DAGGER).build();
 ```
 
 ## Class diagram
+
 ![alt text](./etc/builder.urm.png "Builder class diagram")
 
 ## Applicability
+
 Use the Builder pattern when
 
-* the algorithm for creating a complex object should be independent of the parts that make up the object and how they're assembled
-* the construction process must allow different representations for the object that's constructed
+* The algorithm for creating a complex object should be independent of the parts that make up the object and how they're assembled
+* The construction process must allow different representations for the object that's constructed
 
 ## Real world examples
 

builder/pom.xml

@@ -22,7 +22,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>builder</artifactId>
 	<dependencies>

business-delegate/pom.xml

@@ -22,7 +22,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>business-delegate</artifactId>
 	<dependencies>

bytecode/pom.xml

@@ -20,7 +20,7 @@
 	<parent>
 		<artifactId>java-design-patterns</artifactId>
 		<groupId>com.iluwatar</groupId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<modelVersion>4.0.0</modelVersion>
 

caching/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>caching</artifactId>
   <dependencies>

callback/README.md

@@ -9,14 +9,16 @@ tags:
 ---
 
 ## Intent
-Callback is a piece of executable code that is passed as an argument to other code, which is expected to call back 
-(execute) the argument at some convenient time.
+
+Callback is a piece of executable code that is passed as an argument to other code, which is 
+expected to call back (execute) the argument at some convenient time.
 
 ## Explanation
 
 Real world example
 
-> We need to be notified after executing task has finished. We pass a callback method for the executor and wait for it to call back on us.     
+> We need to be notified after executing task has finished. We pass a callback method for 
+> the executor and wait for it to call back on us.     
 
 In plain words
 
@@ -24,7 +26,9 @@ In plain words
 
 Wikipedia says
 
-> In computer programming, a callback, also known as a "call-after" function, is any executable code that is passed as an argument to other code; that other code is expected to call back (execute) the argument at a given time.
+> In computer programming, a callback, also known as a "call-after" function, is any executable 
+> code that is passed as an argument to other code; that other code is expected to call 
+> back (execute) the argument at a given time.
 
 **Programmatic Example**
 
@@ -61,7 +65,7 @@ public final class SimpleTask extends Task {
 }
 ```
 
-Finally here's how we execute a task and receive a callback when it's finished.
+Finally, here's how we execute a task and receive a callback when it's finished.
 
 ```java
     var task = new SimpleTask();
@@ -69,13 +73,15 @@ Finally here's how we execute a task and receive a callback when it's finished.
 ```
 
 ## Class diagram
+
 ![alt text](./etc/callback.png "Callback")
 
 ## Applicability
+
 Use the Callback pattern when
 
 * when some arbitrary synchronous or asynchronous action must be performed after execution of some defined activity.
 
 ## Real world examples
 
-* [CyclicBarrier](http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CyclicBarrier.html#CyclicBarrier%28int,%20java.lang.Runnable%29) constructor can accept callback that will be triggered every time when barrier is tripped.
+* [CyclicBarrier](http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CyclicBarrier.html#CyclicBarrier%28int,%20java.lang.Runnable%29) constructor can accept a callback that will be triggered every time a barrier is tripped.

callback/etc/callback.urm.puml

@@ -8,11 +8,6 @@ package com.iluwatar.callback {
   interface Callback {
     + call() {abstract}
   }
-  class LambdasApp {
-    - LOGGER : Logger {static}
-    - LambdasApp()
-    + main(args : String[]) {static}
-  }
   class SimpleTask {
     - LOGGER : Logger {static}
     + SimpleTask()

callback/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>callback</artifactId>
   <dependencies>

chain/README.md

@@ -9,27 +9,32 @@ tags:
 ---
 
 ## Intent
-Avoid coupling the sender of a request to its receiver by giving
-more than one object a chance to handle the request. Chain the receiving
-objects and pass the request along the chain until an object handles it.
+Avoid coupling the sender of a request to its receiver by giving more than one object a chance to 
+handle the request. Chain the receiving objects and pass the request along the chain until an object 
+handles it.
 
 ## Explanation
 
 Real world example
 
-> The Orc King gives loud orders to his army. The closest one to react is the commander, then officer and then soldier. The commander, officer and soldier here form a chain of responsibility.
+> The Orc King gives loud orders to his army. The closest one to react is the commander, then 
+> officer and then soldier. The commander, officer and soldier here form a chain of responsibility.
 
 In plain words
 
-> It helps building a chain of objects. Request enters from one end and keeps going from object to object till it finds the suitable handler.
+> It helps to build a chain of objects. A request enters from one end and keeps going from an object 
+> to another until it finds a suitable handler.
 
 Wikipedia says
 
-> In object-oriented design, the chain-of-responsibility pattern is a design pattern consisting of a source of command objects and a series of processing objects. Each processing object contains logic that defines the types of command objects that it can handle; the rest are passed to the next processing object in the chain.
+> In object-oriented design, the chain-of-responsibility pattern is a design pattern consisting of 
+> a source of command objects and a series of processing objects. Each processing object contains 
+> logic that defines the types of command objects that it can handle; the rest are passed to the 
+> next processing object in the chain.
 
 **Programmatic Example**
 
-Translating our example with orcs from above. First we have the request class
+Translating our example with the orcs from above. First we have the `Request` class:
 
 ```java
 public class Request {
@@ -140,14 +145,16 @@ king.makeRequest(new Request(RequestType.COLLECT_TAX, "collect tax")); // Orc so
 ```
 
 ## Class diagram
+
 ![alt text](./etc/chain.urm.png "Chain of Responsibility class diagram")
 
 ## Applicability
+
 Use Chain of Responsibility when
 
-* more than one object may handle a request, and the handler isn't known a priori. The handler should be ascertained automatically
-* you want to issue a request to one of several objects without specifying the receiver explicitly
-* the set of objects that can handle a request should be specified dynamically
+* More than one object may handle a request, and the handler isn't known a priori. The handler should be ascertained automatically.
+* You want to issue a request to one of several objects without specifying the receiver explicitly.
+* The set of objects that can handle a request should be specified dynamically.
 
 ## Real world examples
 

chain/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>chain</artifactId>
   <dependencies>

circuit-breaker/README.md

@@ -12,167 +12,304 @@ tags:
 
 ## Intent
 
-Handle costly remote *procedure/service* calls in such a way that the failure of a **single** service/component cannot bring the whole application down, and we can reconnect to the service as soon as possible.
+Handle costly remote service calls in such a way that the failure of a single service/component 
+cannot bring the whole application down, and we can reconnect to the service as soon as possible.
 
 ## Explanation
 
 Real world example
 
-> Imagine a Web App that has both local (example: files and images) and remote (example: database entries) to serve. The database might not be responding due to a variety of reasons, so if the application keeps trying to read from the database using multiple threads/processes, soon all of them will hang and our entire web application will crash. We should be able to detect this situation and show the user an appropriate message so that he/she can explore other parts of the app unaffected by the database failure without any problem. 
+> Imagine a web application that has both local files/images and remote services that are used for 
+> fetching data. These remote services may be either healthy and responsive at times, or may become 
+> slow and unresponsive at some point of time due to variety of reasons. So if one of the remote 
+> services is slow or not responding successfully, our application will try to fetch response from 
+> the remote service using multiple threads/processes, soon all of them will hang (also called 
+> [thread starvation](https://en.wikipedia.org/wiki/Starvation_(computer_science))) causing our entire web application to crash. We should be able to detect 
+> this situation and show the user an appropriate message so that he/she can explore other parts of 
+> the app unaffected by the remote service failure. Meanwhile, the other services that are working 
+> normally, should keep functioning unaffected by this failure.
 
 In plain words
 
-> Allows us to save resources when we know a remote service failed. Useful when all parts of our application are highly decoupled from each other, and failure of one component doesn't mean the other parts will stop working.
+> Circuit Breaker allows graceful handling of failed remote services. It's especially useful when 
+> all parts of our application are highly decoupled from each other, and failure of one component 
+> doesn't mean the other parts will stop working.
 
 Wikipedia says
 
-> **Circuit breaker** is a design pattern used in modern software development. It is used to detect failures and encapsulates the logic of preventing a failure from constantly recurring, during maintenance, temporary external system failure or unexpected system difficulties.
-
-So, how does this all come together?
+> Circuit breaker is a design pattern used in modern software development. It is used to detect 
+> failures and encapsulates the logic of preventing a failure from constantly recurring, during 
+> maintenance, temporary external system failure or unexpected system difficulties.
 
 ## Programmatic Example
-With the above example in mind we will imitate the functionality in a simple manner. We have two services: A *monitoring service* which will mimic the web app and will make both **local** and **remote** calls.
+
+So, how does this all come together? With the above example in mind we will imitate the 
+functionality in a simple example. A monitoring service mimics the web app and makes both local and 
+remote calls.
 
 The service architecture is as follows:
 
 ![alt text](./etc/ServiceDiagram.PNG "Service Diagram")
 
-In terms of code, the End user application is:
+In terms of code, the end user application is:
 
 ```java
 public class App {
-   
+
   private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
-    
+
+  /**
+   * Program entry point.
+   *
+   * @param args command line args
+   */
   public static void main(String[] args) {
-    var obj = new MonitoringService();
-    var circuitBreaker = new CircuitBreaker(3000, 1, 2000 * 1000 * 1000); 
+
     var serverStartTime = System.nanoTime();
-    while (true) {
-      LOGGER.info(obj.localResourceResponse());
-      LOGGER.info(obj.remoteResourceResponse(circuitBreaker, serverStartTime));
-      LOGGER.info(circuitBreaker.getState());
-      try {
-        Thread.sleep(5 * 1000); 
-      } catch (InterruptedException e) {
-        LOGGER.error(e.getMessage());
-      }
+
+    var delayedService = new DelayedRemoteService(serverStartTime, 5);
+    var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000, 2,
+        2000 * 1000 * 1000);
+
+    var quickService = new QuickRemoteService();
+    var quickServiceCircuitBreaker = new DefaultCircuitBreaker(quickService, 3000, 2,
+        2000 * 1000 * 1000);
+
+    //Create an object of monitoring service which makes both local and remote calls
+    var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,
+        quickServiceCircuitBreaker);
+
+    //Fetch response from local resource
+    LOGGER.info(monitoringService.localResourceResponse());
+
+    //Fetch response from delayed service 2 times, to meet the failure threshold
+    LOGGER.info(monitoringService.delayedServiceResponse());
+    LOGGER.info(monitoringService.delayedServiceResponse());
+
+    //Fetch current state of delayed service circuit breaker after crossing failure threshold limit
+    //which is OPEN now
+    LOGGER.info(delayedServiceCircuitBreaker.getState());
+
+    //Meanwhile, the delayed service is down, fetch response from the healthy quick service
+    LOGGER.info(monitoringService.quickServiceResponse());
+    LOGGER.info(quickServiceCircuitBreaker.getState());
+
+    //Wait for the delayed service to become responsive
+    try {
+      LOGGER.info("Waiting for delayed service to become responsive");
+      Thread.sleep(5000);
+    } catch (InterruptedException e) {
+      e.printStackTrace();
     }
+    //Check the state of delayed circuit breaker, should be HALF_OPEN
+    LOGGER.info(delayedServiceCircuitBreaker.getState());
+
+    //Fetch response from delayed service, which should be healthy by now
+    LOGGER.info(monitoringService.delayedServiceResponse());
+    //As successful response is fetched, it should be CLOSED again.
+    LOGGER.info(delayedServiceCircuitBreaker.getState());
   }
 }
 ```
 
-The monitoring service is: 
+The monitoring service: 
 
-``` java
+```java
 public class MonitoringService {
 
+  private final CircuitBreaker delayedService;
+
+  private final CircuitBreaker quickService;
+
+  public MonitoringService(CircuitBreaker delayedService, CircuitBreaker quickService) {
+    this.delayedService = delayedService;
+    this.quickService = quickService;
+  }
+
+  //Assumption: Local service won't fail, no need to wrap it in a circuit breaker logic
   public String localResourceResponse() {
     return "Local Service is working";
   }
 
-  public String remoteResourceResponse(CircuitBreaker circuitBreaker, long serverStartTime) {
+  /**
+   * Fetch response from the delayed service (with some simulated startup time).
+   *
+   * @return response string
+   */
+  public String delayedServiceResponse() {
     try {
-      return circuitBreaker.call("delayedService", serverStartTime);
-    } catch (Exception e) {
+      return this.delayedService.attemptRequest();
+    } catch (RemoteServiceException e) {
+      return e.getMessage();
+    }
+  }
+
+  /**
+   * Fetches response from a healthy service without any failure.
+   *
+   * @return response string
+   */
+  public String quickServiceResponse() {
+    try {
+      return this.quickService.attemptRequest();
+    } catch (RemoteServiceException e) {
       return e.getMessage();
     }
   }
 }
 ```
-As it can be seen, it does the call to get local resources directly, but it wraps the call to remote (costly) service in a circuit breaker object, which prevents faults as follows:
+As it can be seen, it does the call to get local resources directly, but it wraps the call to 
+remote (costly) service in a circuit breaker object, which prevents faults as follows:
 
 ```java
-public class CircuitBreaker {
+public class DefaultCircuitBreaker implements CircuitBreaker {
+
   private final long timeout;
   private final long retryTimePeriod;
+  private final RemoteService service;
   long lastFailureTime;
+  private String lastFailureResponse;
   int failureCount;
   private final int failureThreshold;
   private State state;
   private final long futureTime = 1000 * 1000 * 1000 * 1000;
 
-  CircuitBreaker(long timeout, int failureThreshold, long retryTimePeriod) {
+  /**
+   * Constructor to create an instance of Circuit Breaker.
+   *
+   * @param timeout          Timeout for the API request. Not necessary for this simple example
+   * @param failureThreshold Number of failures we receive from the depended service before changing
+   *                         state to 'OPEN'
+   * @param retryTimePeriod  Time period after which a new request is made to remote service for
+   *                         status check.
+   */
+  DefaultCircuitBreaker(RemoteService serviceToCall, long timeout, int failureThreshold,
+      long retryTimePeriod) {
+    this.service = serviceToCall;
+    // We start in a closed state hoping that everything is fine
     this.state = State.CLOSED;
     this.failureThreshold = failureThreshold;
+    // Timeout for the API request.
+    // Used to break the calls made to remote resource if it exceeds the limit
     this.timeout = timeout;
     this.retryTimePeriod = retryTimePeriod;
+    //An absurd amount of time in future which basically indicates the last failure never happened
     this.lastFailureTime = System.nanoTime() + futureTime;
     this.failureCount = 0;
   }
-    
-  private void reset() {
+
+  // Reset everything to defaults
+  @Override
+  public void recordSuccess() {
     this.failureCount = 0;
-    this.lastFailureTime = System.nanoTime() + futureTime; 
+    this.lastFailureTime = System.nanoTime() + futureTime;
     this.state = State.CLOSED;
   }
 
-  private void recordFailure() {
+  @Override
+  public void recordFailure(String response) {
     failureCount = failureCount + 1;
     this.lastFailureTime = System.nanoTime();
+    // Cache the failure response for returning on open state
+    this.lastFailureResponse = response;
   }
-    
-  protected void setState() {
-    if (failureCount > failureThreshold) { 
+
+  // Evaluate the current state based on failureThreshold, failureCount and lastFailureTime.
+  protected void evaluateState() {
+    if (failureCount >= failureThreshold) { //Then something is wrong with remote service
       if ((System.nanoTime() - lastFailureTime) > retryTimePeriod) {
+        //We have waited long enough and should try checking if service is up
         state = State.HALF_OPEN;
       } else {
+        //Service would still probably be down
         state = State.OPEN;
       }
     } else {
+      //Everything is working fine
       state = State.CLOSED;
     }
   }
-    
+
+  @Override
   public String getState() {
+    evaluateState();
     return state.name();
   }
-  
-  public void setStateForBypass(State state) {
+
+  /**
+   * Break the circuit beforehand if it is known service is down Or connect the circuit manually if
+   * service comes online before expected.
+   *
+   * @param state State at which circuit is in
+   */
+  @Override
+  public void setState(State state) {
     this.state = state;
+    switch (state) {
+      case OPEN:
+        this.failureCount = failureThreshold;
+        this.lastFailureTime = System.nanoTime();
+        break;
+      case HALF_OPEN:
+        this.failureCount = failureThreshold;
+        this.lastFailureTime = System.nanoTime() - retryTimePeriod;
+        break;
+      default:
+        this.failureCount = 0;
+    }
   }
-   
-  public String call(String serviceToCall, long serverStartTime) throws Exception {
-    setState();
+
+  /**
+   * Executes service call.
+   *
+   * @return Value from the remote resource, stale response or a custom exception
+   */
+  @Override
+  public String attemptRequest() throws RemoteServiceException {
+    evaluateState();
     if (state == State.OPEN) {
-      return "This is stale response from API";
+      // return cached response if the circuit is in OPEN state
+      return this.lastFailureResponse;
     } else {
-      if (serviceToCall.equals("delayedService")) {
-        var delayedService = new DelayedService(20);
-        var response = delayedService.response(serverStartTime);
-        if (response.split(" ")[3].equals("working")) {
-          reset();
-          return response;
-        } else {
-          recordFailure();
-          throw new Exception("Remote service not responding");
-        }
-      } else {
-        throw new Exception("Unknown Service Name");
+      // Make the API request if the circuit is not OPEN
+      try {
+        //In a real application, this would be run in a thread and the timeout
+        //parameter of the circuit breaker would be utilized to know if service
+        //is working. Here, we simulate that based on server response itself
+        var response = service.call();
+        // Yay!! the API responded fine. Let's reset everything.
+        recordSuccess();
+        return response;
+      } catch (RemoteServiceException ex) {
+        recordFailure(ex.getMessage());
+        throw ex;
       }
     }
   }
 }
 ```
 
-How does the above pattern prevent failures? Let's understand via this finite state machine implemented by it.
+How does the above pattern prevent failures? Let's understand via this finite state machine 
+implemented by it.
 
 ![alt text](./etc/StateDiagram.PNG "State Diagram")
 
-- We initialize the Circuit Breaker object with certain parameters: **timeout**, **failureThreshold** and **retryTimePeriod** which help determine how resilient the API is.
-- Initially, we are in the **closed** state and the remote call to API happens.
+- We initialize the Circuit Breaker object with certain parameters: `timeout`, `failureThreshold` and `retryTimePeriod` which help determine how resilient the API is.
+- Initially, we are in the `closed` state and nos remote calls to the API have occurred.
 - Every time the call succeeds, we reset the state to as it was in the beginning.
-- If the number of failures cross a certain threshold, we move to the **open** state, which acts just like an open circuit and prevents remote service calls from being made, thus saving resources. (Here, we return the response called ```stale response from API```)
-- Once we exceed the retry timeout period, we move to the **half-open** state and make another call to the remote service again to check if the service is working so that we can serve fresh content. A *failure* sets it back to **open** state and another attempt is made after retry timeout period, while a *success* sets it to **closed** state so that everything starts working normally again. 
+- If the number of failures cross a certain threshold, we move to the `open` state, which acts just like an open circuit and prevents remote service calls from being made, thus saving resources. (Here, we return the response called ```stale response from API```)
+- Once we exceed the retry timeout period, we move to the `half-open` state and make another call to the remote service again to check if the service is working so that we can serve fresh content. A failure sets it back to `open` state and another attempt is made after retry timeout period, while a success sets it to `closed` state so that everything starts working normally again. 
 
 ## Class diagram
+
 ![alt text](./etc/circuit-breaker.urm.png "Circuit Breaker class diagram")
 
 ## Applicability
+
 Use the Circuit Breaker pattern when
 
 - Building a fault-tolerant application where failure of some services shouldn't bring the entire application down.
-- Building an continuously incremental/continuous delivery application, as some of it's components can be upgraded without shutting it down entirely.
+- Building a continuously running (always-on) application, so that its components can be upgraded without shutting it down entirely.
 
 ## Related Patterns
 

circuit-breaker/etc/circuit-breaker.urm.puml

@@ -5,32 +5,52 @@ package com.iluwatar.circuitbreaker {
     + App()
     + main(args : String[]) {static}
   }
-  class CircuitBreaker {
+  interface CircuitBreaker {
+    + attemptRequest() : String {abstract}
+    + getState() : String {abstract}
+    + recordFailure(String) {abstract}
+    + recordSuccess() {abstract}
+    + setState(State) {abstract}
+  }
+  class DefaultCircuitBreaker {
     ~ failureCount : int
     - failureThreshold : int
     - futureTime : long
+    - lastFailureResponse : String
     ~ lastFailureTime : long
     - retryTimePeriod : long
+    - service : RemoteService
     - state : State
     - timeout : long
-    ~ CircuitBreaker(timeout : long, failureThreshold : int, retryTimePeriod : long)
-    + call(serviceToCall : String, serverStartTime : long) : String
+    ~ DefaultCircuitBreaker(serviceToCall : RemoteService, timeout : long, failureThreshold : int, retryTimePeriod : long)
+    + attemptRequest() : String
+    # evaluateState()
     + getState() : String
-    - recordFailure()
-    - reset()
-    # setState()
-    + setStateForBypass(state : State)
+    + recordFailure(response : String)
+    + recordSuccess()
+    + setState(state : State)
   }
-  class DelayedService {
+  class DelayedRemoteService {
     - delay : int
-    + DelayedService()
-    + DelayedService(delay : int)
-    + response(serverStartTime : long) : String
+    - serverStartTime : long
+    + DelayedRemoteService()
+    + DelayedRemoteService(serverStartTime : long, delay : int)
+    + call() : String
   }
   class MonitoringService {
-    + MonitoringService()
+    - delayedService : CircuitBreaker
+    - quickService : CircuitBreaker
+    + MonitoringService(delayedService : CircuitBreaker, quickService : CircuitBreaker)
+    + delayedServiceResponse() : String
     + localResourceResponse() : String
-    + remoteResourceResponse(circuitBreaker : CircuitBreaker, serverStartTime : long) : String
+    + quickServiceResponse() : String
+  }
+  class QuickRemoteService {
+    + QuickRemoteService()
+    + call() : String
+  }
+  interface RemoteService {
+    + call() : String {abstract}
   }
   enum State {
     + CLOSED {static}
@@ -40,5 +60,10 @@ package com.iluwatar.circuitbreaker {
     + values() : State[] {static}
   }
 }
-CircuitBreaker -->  "-state" State
+DefaultCircuitBreaker -->  "-state" State
+MonitoringService -->  "-delayedService" CircuitBreaker
+DefaultCircuitBreaker -->  "-service" RemoteService
+DefaultCircuitBreaker ..|> CircuitBreaker 
+DelayedRemoteService ..|> RemoteService 
+QuickRemoteService ..|> RemoteService 
 @enduml

circuit-breaker/pom.xml

@@ -27,7 +27,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.23.0-SNAPSHOT</version>
+        <version>1.24.0-SNAPSHOT</version>
     </parent>
     <artifactId>circuit-breaker</artifactId>
     <dependencies>

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/App.java

@@ -36,17 +36,18 @@ import org.slf4j.LoggerFactory;
  * operational again, so that we can use it
  * </p>
  * <p>
- * In this example, the circuit breaker pattern is demonstrated by using two services: {@link
- * MonitoringService} and {@link DelayedService}. The monitoring service is responsible for calling
- * two services: a local service and a remote service {@link DelayedService} , and by using the
- * circuit breaker construction we ensure that if the call to remote service is going to fail, we
- * are going to save our resources and not make the function call at all, by wrapping our call to
- * the remote service in the circuit breaker object.
+ * In this example, the circuit breaker pattern is demonstrated by using three services: {@link
+ * DelayedRemoteService}, {@link QuickRemoteService} and {@link MonitoringService}. The monitoring
+ * service is responsible for calling three services: a local service, a quick remove service
+ * {@link QuickRemoteService} and a delayed remote service {@link DelayedRemoteService} , and by
+ * using the circuit breaker construction we ensure that if the call to remote service is going to
+ * fail, we are going to save our resources and not make the function call at all, by wrapping our
+ * call to the remote services in the {@link DefaultCircuitBreaker} implementation object.
  * </p>
  * <p>
- * This works as follows: The {@link CircuitBreaker} object can be in one of three states:
- * <b>Open</b>, <b>Closed</b> and <b>Half-Open</b>, which represents the real world circuits. If the
- * state is closed (initial), we assume everything is alright and perform the function call.
+ * This works as follows: The {@link DefaultCircuitBreaker} object can be in one of three states:
+ * <b>Open</b>, <b>Closed</b> and <b>Half-Open</b>, which represents the real world circuits. If
+ * the state is closed (initial), we assume everything is alright and perform the function call.
  * However, every time the call fails, we note it and once it crosses a threshold, we set the state
  * to Open, preventing any further calls to the remote server. Then, after a certain retry period
  * (during which we expect thee service to recover), we make another call to the remote server and
@@ -63,22 +64,50 @@ public class App {
    *
    * @param args command line args
    */
-  @SuppressWarnings("squid:S2189")
   public static void main(String[] args) {
-    //Create an object of monitoring service which makes both local and remote calls
-    var obj = new MonitoringService();
-    //Set the circuit Breaker parameters
-    var circuitBreaker = new CircuitBreaker(3000, 1, 2000 * 1000 * 1000);
+
     var serverStartTime = System.nanoTime();
-    while (true) {
-      LOGGER.info(obj.localResourceResponse());
-      LOGGER.info(obj.remoteResourceResponse(circuitBreaker, serverStartTime));
-      LOGGER.info(circuitBreaker.getState());
-      try {
-        Thread.sleep(5 * 1000);
-      } catch (InterruptedException e) {
-        LOGGER.error(e.getMessage());
-      }
+
+    var delayedService = new DelayedRemoteService(serverStartTime, 5);
+    var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000, 2,
+        2000 * 1000 * 1000);
+
+    var quickService = new QuickRemoteService();
+    var quickServiceCircuitBreaker = new DefaultCircuitBreaker(quickService, 3000, 2,
+        2000 * 1000 * 1000);
+
+    //Create an object of monitoring service which makes both local and remote calls
+    var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,
+        quickServiceCircuitBreaker);
+
+    //Fetch response from local resource
+    LOGGER.info(monitoringService.localResourceResponse());
+
+    //Fetch response from delayed service 2 times, to meet the failure threshold
+    LOGGER.info(monitoringService.delayedServiceResponse());
+    LOGGER.info(monitoringService.delayedServiceResponse());
+
+    //Fetch current state of delayed service circuit breaker after crossing failure threshold limit
+    //which is OPEN now
+    LOGGER.info(delayedServiceCircuitBreaker.getState());
+
+    //Meanwhile, the delayed service is down, fetch response from the healthy quick service
+    LOGGER.info(monitoringService.quickServiceResponse());
+    LOGGER.info(quickServiceCircuitBreaker.getState());
+
+    //Wait for the delayed service to become responsive
+    try {
+      LOGGER.info("Waiting for delayed service to become responsive");
+      Thread.sleep(5000);
+    } catch (InterruptedException e) {
+      e.printStackTrace();
     }
+    //Check the state of delayed circuit breaker, should be HALF_OPEN
+    LOGGER.info(delayedServiceCircuitBreaker.getState());
+
+    //Fetch response from delayed service, which should be healthy by now
+    LOGGER.info(monitoringService.delayedServiceResponse());
+    //As successful response is fetched, it should be CLOSED again.
+    LOGGER.info(delayedServiceCircuitBreaker.getState());
   }
 }

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/CircuitBreaker.java

@@ -24,114 +24,22 @@
 package com.iluwatar.circuitbreaker;
 
 /**
- * The circuit breaker class with all configurations.
+ * The Circuit breaker interface.
  */
-public class CircuitBreaker {
-  private final long timeout;
-  private final long retryTimePeriod;
-  long lastFailureTime;
-  int failureCount;
-  private final int failureThreshold;
-  private State state;
-  private final long futureTime = 1000 * 1000 * 1000 * 1000;
+public interface CircuitBreaker {
 
-  /**
-   * Constructor to create an instance of Circuit Breaker.
-   *
-   * @param timeout          Timeout for the API request. Not necessary for this simple example
-   * @param failureThreshold Number of failures we receive from the depended service before changing
-   *                         state to 'OPEN'
-   * @param retryTimePeriod  Time period after which a new request is made to remote service for
-   *                         status check.
-   */
-  CircuitBreaker(long timeout, int failureThreshold, long retryTimePeriod) {
-    // We start in a closed state hoping that everything is fine
-    this.state = State.CLOSED;
-    this.failureThreshold = failureThreshold;
-    // Timeout for the API request.
-    // Used to break the calls made to remote resource if it exceeds the limit
-    this.timeout = timeout;
-    this.retryTimePeriod = retryTimePeriod;
-    //An absurd amount of time in future which basically indicates the last failure never happened
-    this.lastFailureTime = System.nanoTime() + futureTime;
-    this.failureCount = 0;
-  }
+  // Success response. Reset everything to defaults
+  void recordSuccess();
 
-  //Reset everything to defaults
-  private void reset() {
-    this.failureCount = 0;
-    this.lastFailureTime = System.nanoTime() + futureTime;
-    this.state = State.CLOSED;
-  }
+  // Failure response. Handle accordingly with response and change state if required.
+  void recordFailure(String response);
 
-  private void recordFailure() {
-    failureCount = failureCount + 1;
-    this.lastFailureTime = System.nanoTime();
-  }
+  // Get the current state of circuit breaker
+  String getState();
 
-  protected void setState() {
-    if (failureCount > failureThreshold) { //Then something is wrong with remote service
-      if ((System.nanoTime() - lastFailureTime) > retryTimePeriod) {
-        //We have waited long enough and should try checking if service is up
-        state = State.HALF_OPEN;
-      } else {
-        //Service would still probably be down
-        state = State.OPEN;
-      }
-    } else {
-      //Everything is working fine
-      state = State.CLOSED;
-    }
-  }
+  // Set the specific state manually.
+  void setState(State state);
 
-  public String getState() {
-    return state.name();
-  }
-
-  /**
-   * Break the circuit beforehand if it is known service is down Or connect the circuit manually if
-   * service comes online before expected.
-   *
-   * @param state State at which circuit is in
-   */
-  public void setStateForBypass(State state) {
-    this.state = state;
-  }
-
-  /**
-   * Executes service call.
-   *
-   * @param serviceToCall   The name of the service in String. Can be changed to data URLs in case
-   *                        of web applications
-   * @param serverStartTime Time at which actual server was started which makes calls to this
-   *                        service
-   * @return Value from the remote resource, stale response or a custom exception
-   */
-  public String call(String serviceToCall, long serverStartTime) throws Exception {
-    setState();
-    if (state == State.OPEN) {
-      // return  cached response if no the circuit is in OPEN state
-      return "This is stale response from API";
-    } else {
-      // Make the API request if the circuit is not OPEN
-      if (serviceToCall.equals("delayedService")) {
-        var delayedService = new DelayedService(20);
-        var response = delayedService.response(serverStartTime);
-        //In a real application, this would be run in a thread and the timeout
-        //parameter of the circuit breaker would be utilized to know if service
-        //is working. Here, we simulate that based on server response itself
-        if (response.split(" ")[3].equals("working")) {
-          // Yay!! the API responded fine. Let's reset everything.
-          reset();
-          return response;
-        } else {
-          // Uh-oh!! the call still failed. Let's update that in our records.
-          recordFailure();
-          throw new Exception("Remote service not responding");
-        }
-      } else {
-        throw new Exception("Unknown Service Name");
-      }
-    }
-  }
-}
+  // Attempt to fetch response from the remote service.
+  String attemptRequest() throws RemoteServiceException;
+}

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/DefaultCircuitBreaker.java

@@ -0,0 +1,155 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.circuitbreaker;
+
+/**
+ * The delay based Circuit breaker implementation that works in a
+ * CLOSED->OPEN-(retry_time_period)->HALF_OPEN->CLOSED flow with some retry time period for failed
+ * services and a failure threshold for service to open circuit.
+ */
+public class DefaultCircuitBreaker implements CircuitBreaker {
+
+  private final long timeout;
+  private final long retryTimePeriod;
+  private final RemoteService service;
+  long lastFailureTime;
+  private String lastFailureResponse;
+  int failureCount;
+  private final int failureThreshold;
+  private State state;
+  private final long futureTime = 1000 * 1000 * 1000 * 1000;
+
+  /**
+   * Constructor to create an instance of Circuit Breaker.
+   *
+   * @param timeout          Timeout for the API request. Not necessary for this simple example
+   * @param failureThreshold Number of failures we receive from the depended service before changing
+   *                         state to 'OPEN'
+   * @param retryTimePeriod  Time period after which a new request is made to remote service for
+   *                         status check.
+   */
+  DefaultCircuitBreaker(RemoteService serviceToCall, long timeout, int failureThreshold,
+      long retryTimePeriod) {
+    this.service = serviceToCall;
+    // We start in a closed state hoping that everything is fine
+    this.state = State.CLOSED;
+    this.failureThreshold = failureThreshold;
+    // Timeout for the API request.
+    // Used to break the calls made to remote resource if it exceeds the limit
+    this.timeout = timeout;
+    this.retryTimePeriod = retryTimePeriod;
+    //An absurd amount of time in future which basically indicates the last failure never happened
+    this.lastFailureTime = System.nanoTime() + futureTime;
+    this.failureCount = 0;
+  }
+
+  // Reset everything to defaults
+  @Override
+  public void recordSuccess() {
+    this.failureCount = 0;
+    this.lastFailureTime = System.nanoTime() + futureTime;
+    this.state = State.CLOSED;
+  }
+
+  @Override
+  public void recordFailure(String response) {
+    failureCount = failureCount + 1;
+    this.lastFailureTime = System.nanoTime();
+    // Cache the failure response for returning on open state
+    this.lastFailureResponse = response;
+  }
+
+  // Evaluate the current state based on failureThreshold, failureCount and lastFailureTime.
+  protected void evaluateState() {
+    if (failureCount >= failureThreshold) { //Then something is wrong with remote service
+      if ((System.nanoTime() - lastFailureTime) > retryTimePeriod) {
+        //We have waited long enough and should try checking if service is up
+        state = State.HALF_OPEN;
+      } else {
+        //Service would still probably be down
+        state = State.OPEN;
+      }
+    } else {
+      //Everything is working fine
+      state = State.CLOSED;
+    }
+  }
+
+  @Override
+  public String getState() {
+    evaluateState();
+    return state.name();
+  }
+
+  /**
+   * Break the circuit beforehand if it is known service is down Or connect the circuit manually if
+   * service comes online before expected.
+   *
+   * @param state State at which circuit is in
+   */
+  @Override
+  public void setState(State state) {
+    this.state = state;
+    switch (state) {
+      case OPEN:
+        this.failureCount = failureThreshold;
+        this.lastFailureTime = System.nanoTime();
+        break;
+      case HALF_OPEN:
+        this.failureCount = failureThreshold;
+        this.lastFailureTime = System.nanoTime() - retryTimePeriod;
+        break;
+      default:
+        this.failureCount = 0;
+    }
+  }
+
+  /**
+   * Executes service call.
+   *
+   * @return Value from the remote resource, stale response or a custom exception
+   */
+  @Override
+  public String attemptRequest() throws RemoteServiceException {
+    evaluateState();
+    if (state == State.OPEN) {
+      // return cached response if the circuit is in OPEN state
+      return this.lastFailureResponse;
+    } else {
+      // Make the API request if the circuit is not OPEN
+      try {
+        //In a real application, this would be run in a thread and the timeout
+        //parameter of the circuit breaker would be utilized to know if service
+        //is working. Here, we simulate that based on server response itself
+        var response = service.call();
+        // Yay!! the API responded fine. Let's reset everything.
+        recordSuccess();
+        return response;
+      } catch (RemoteServiceException ex) {
+        recordFailure(ex.getMessage());
+        throw ex;
+      }
+    }
+  }
+}

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/DelayedRemoteService.java

@@ -27,7 +27,9 @@ package com.iluwatar.circuitbreaker;
  * This simulates the remote service It responds only after a certain timeout period (default set to
  * 20 seconds).
  */
-public class DelayedService {
+public class DelayedRemoteService implements RemoteService {
+
+  private final long serverStartTime;
   private final int delay;
 
   /**
@@ -35,22 +37,23 @@ public class DelayedService {
    *
    * @param delay the delay after which service would behave properly, in seconds
    */
-  public DelayedService(int delay) {
+  public DelayedRemoteService(long serverStartTime, int delay) {
+    this.serverStartTime = serverStartTime;
     this.delay = delay;
   }
 
-  public DelayedService() {
-    this.delay = 60;
+  public DelayedRemoteService() {
+    this.serverStartTime = System.nanoTime();
+    this.delay = 20;
   }
 
   /**
    * Responds based on delay, current time and server start time if the service is down / working.
    *
-   * @param serverStartTime Time at which actual server was started which makes calls to this
-   *                        service
    * @return The state of the service
    */
-  public String response(long serverStartTime) {
+  @Override
+  public String call() throws RemoteServiceException {
     var currentTime = System.nanoTime();
     //Since currentTime and serverStartTime are both in nanoseconds, we convert it to
     //seconds by diving by 10e9 and ensure floating point division by multiplying it
@@ -58,9 +61,8 @@ public class DelayedService {
     //send the reply
     if ((currentTime - serverStartTime) * 1.0 / (1000 * 1000 * 1000) < delay) {
       //Can use Thread.sleep() here to block and simulate a hung server
-      return "Delayed service is down";
-    } else {
-      return "Delayed service is working";
+      throw new RemoteServiceException("Delayed service is down");
     }
+    return "Delayed service is working";
   }
 }

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/MonitoringService.java

@@ -24,28 +24,47 @@
 package com.iluwatar.circuitbreaker;
 
 /**
- * The service class which makes local and remote calls Uses {@link CircuitBreaker} object to ensure
- * remote calls don't use up resources.
+ * The service class which makes local and remote calls Uses {@link DefaultCircuitBreaker} object to
+ * ensure remote calls don't use up resources.
  */
 public class MonitoringService {
 
+  private final CircuitBreaker delayedService;
+
+  private final CircuitBreaker quickService;
+
+  public MonitoringService(CircuitBreaker delayedService, CircuitBreaker quickService) {
+    this.delayedService = delayedService;
+    this.quickService = quickService;
+  }
+
   //Assumption: Local service won't fail, no need to wrap it in a circuit breaker logic
   public String localResourceResponse() {
     return "Local Service is working";
   }
 
   /**
-   * Try to get result from remote server.
+   * Fetch response from the delayed service (with some simulated startup time).
    *
-   * @param circuitBreaker  The circuitBreaker object with all parameters
-   * @param serverStartTime Time at which actual server was started which makes calls to this
-   *                        service
-   * @return result from the remote response or exception raised by it.
+   * @return response string
    */
-  public String remoteResourceResponse(CircuitBreaker circuitBreaker, long serverStartTime) {
+  public String delayedServiceResponse() {
     try {
-      return circuitBreaker.call("delayedService", serverStartTime);
-    } catch (Exception e) {
+      return this.delayedService.attemptRequest();
+    } catch (RemoteServiceException e) {
+      return e.getMessage();
+    }
+  }
+
+  /**
+   * Fetches response from a healthy service without any failure.
+   *
+   * @return response string
+   */
+  public String quickServiceResponse() {
+    try {
+      return this.quickService.attemptRequest();
+    } catch (RemoteServiceException e) {
       return e.getMessage();
     }
   }

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/QuickRemoteService.java

@@ -0,0 +1,35 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.circuitbreaker;
+
+/**
+ * A quick response remote service, that responds healthy without any delay or failure.
+ */
+public class QuickRemoteService implements RemoteService {
+
+  @Override
+  public String call() throws RemoteServiceException {
+    return "Quick Service is working";
+  }
+}

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/RemoteService.java

@@ -0,0 +1,34 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.circuitbreaker;
+
+/**
+ * The Remote service interface, used by {@link CircuitBreaker} for fetching response from remote
+ * services.
+ */
+public interface RemoteService {
+
+  //Fetch response from remote service.
+  String call() throws RemoteServiceException;
+}

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/RemoteServiceException.java

@@ -0,0 +1,34 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.circuitbreaker;
+
+/**
+ * Exception thrown when {@link RemoteService} does not respond successfully.
+ */
+public class RemoteServiceException extends Exception {
+
+  public RemoteServiceException(String message) {
+    super(message);
+  }
+}

circuit-breaker/src/test/java/com/iluwatar/circuitbreaker/AppTest.java

@@ -0,0 +1,135 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.circuitbreaker;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * App Test showing usage of circuit breaker.
+ */
+public class AppTest {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(AppTest.class);
+
+  //Startup delay for delayed service (in seconds)
+  private static final int STARTUP_DELAY = 4;
+
+  //Number of failed requests for circuit breaker to open
+  private static final int FAILURE_THRESHOLD = 1;
+
+  //Time period in seconds for circuit breaker to retry service
+  private static final int RETRY_PERIOD = 2;
+
+  private MonitoringService monitoringService;
+
+  private CircuitBreaker delayedServiceCircuitBreaker;
+
+  private CircuitBreaker quickServiceCircuitBreaker;
+
+  /**
+   * Setup the circuit breakers and services, where {@link DelayedRemoteService} will be start with
+   * a delay of 4 seconds and a {@link QuickRemoteService} responding healthy. Both services are
+   * wrapped in a {@link DefaultCircuitBreaker} implementation with failure threshold of 1 failure
+   * and retry time period of 2 seconds.
+   */
+  @BeforeEach
+  public void setupCircuitBreakers() {
+    var delayedService = new DelayedRemoteService(System.nanoTime(), STARTUP_DELAY);
+    //Set the circuit Breaker parameters
+    delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000,
+        FAILURE_THRESHOLD,
+        RETRY_PERIOD * 1000 * 1000 * 1000);
+
+    var quickService = new QuickRemoteService();
+    //Set the circuit Breaker parameters
+    quickServiceCircuitBreaker = new DefaultCircuitBreaker(quickService, 3000, FAILURE_THRESHOLD,
+        RETRY_PERIOD * 1000 * 1000 * 1000);
+
+    monitoringService = new MonitoringService(delayedServiceCircuitBreaker,
+        quickServiceCircuitBreaker);
+
+  }
+
+  @Test
+  public void testFailure_OpenStateTransition() {
+    //Calling delayed service, which will be unhealthy till 4 seconds
+    assertEquals("Delayed service is down", monitoringService.delayedServiceResponse());
+    //As failure threshold is "1", the circuit breaker is changed to OPEN
+    assertEquals("OPEN", delayedServiceCircuitBreaker.getState());
+    //As circuit state is OPEN, we expect a quick fallback response from circuit breaker.
+    assertEquals("Delayed service is down", monitoringService.delayedServiceResponse());
+
+    //Meanwhile, the quick service is responding and the circuit state is CLOSED
+    assertEquals("Quick Service is working", monitoringService.quickServiceResponse());
+    assertEquals("CLOSED", quickServiceCircuitBreaker.getState());
+
+  }
+
+  @Test
+  public void testFailure_HalfOpenStateTransition() {
+    //Calling delayed service, which will be unhealthy till 4 seconds
+    assertEquals("Delayed service is down", monitoringService.delayedServiceResponse());
+    //As failure threshold is "1", the circuit breaker is changed to OPEN
+    assertEquals("OPEN", delayedServiceCircuitBreaker.getState());
+
+    //Waiting for recovery period of 2 seconds for circuit breaker to retry service.
+    try {
+      LOGGER.info("Waiting 2s for delayed service to become responsive");
+      Thread.sleep(2000);
+    } catch (InterruptedException e) {
+      e.printStackTrace();
+    }
+    //After 2 seconds, the circuit breaker should move to "HALF_OPEN" state and retry fetching response from service again
+    assertEquals("HALF_OPEN", delayedServiceCircuitBreaker.getState());
+
+  }
+
+  @Test
+  public void testRecovery_ClosedStateTransition() {
+    //Calling delayed service, which will be unhealthy till 4 seconds
+    assertEquals("Delayed service is down", monitoringService.delayedServiceResponse());
+    //As failure threshold is "1", the circuit breaker is changed to OPEN
+    assertEquals("OPEN", delayedServiceCircuitBreaker.getState());
+
+    //Waiting for 4 seconds, which is enough for DelayedService to become healthy and respond successfully.
+    try {
+      LOGGER.info("Waiting 4s for delayed service to become responsive");
+      Thread.sleep(4000);
+    } catch (InterruptedException e) {
+      e.printStackTrace();
+    }
+    //As retry period is 2 seconds (<4 seconds of wait), hence the circuit breaker should be back in HALF_OPEN state.
+    assertEquals("HALF_OPEN", delayedServiceCircuitBreaker.getState());
+    //Check the success response from delayed service.
+    assertEquals("Delayed service is working", monitoringService.delayedServiceResponse());
+    //As the response is success, the state should be CLOSED
+    assertEquals("CLOSED", delayedServiceCircuitBreaker.getState());
+  }
+
+}

circuit-breaker/src/test/java/com/iluwatar/circuitbreaker/DefaultCircuitBreakerTest.java

@@ -25,56 +25,60 @@ package com.iluwatar.circuitbreaker;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import java.rmi.Remote;
 import org.junit.jupiter.api.Test;
 
 /**
  * Circuit Breaker test
  */
-public class CircuitBreakerTest {
+public class DefaultCircuitBreakerTest {
 
   //long timeout, int failureThreshold, long retryTimePeriod
   @Test
-  public void testSetState() {
-    var circuitBreaker = new CircuitBreaker(1, 1, 100);
+  public void testEvaluateState() {
+    var circuitBreaker = new DefaultCircuitBreaker(null, 1, 1, 100);
     //Right now, failureCount<failureThreshold, so state should be closed
     assertEquals(circuitBreaker.getState(), "CLOSED");
     circuitBreaker.failureCount = 4;
     circuitBreaker.lastFailureTime = System.nanoTime();
-    circuitBreaker.setState();
+    circuitBreaker.evaluateState();
     //Since failureCount>failureThreshold, and lastFailureTime is nearly equal to current time,
     //state should be half-open
     assertEquals(circuitBreaker.getState(), "HALF_OPEN");
     //Since failureCount>failureThreshold, and lastFailureTime is much lesser current time,
     //state should be open
     circuitBreaker.lastFailureTime = System.nanoTime() - 1000 * 1000 * 1000 * 1000;
-    circuitBreaker.setState();
+    circuitBreaker.evaluateState();
     assertEquals(circuitBreaker.getState(), "OPEN");
     //Now set it back again to closed to test idempotency
     circuitBreaker.failureCount = 0;
-    circuitBreaker.setState();
+    circuitBreaker.evaluateState();
     assertEquals(circuitBreaker.getState(), "CLOSED");
   }
 
   @Test
   public void testSetStateForBypass() {
-    var circuitBreaker = new CircuitBreaker(1, 1, 100);
+    var circuitBreaker = new DefaultCircuitBreaker(null, 1, 1, 2000 * 1000 * 1000);
     //Right now, failureCount<failureThreshold, so state should be closed
     //Bypass it and set it to open
-    circuitBreaker.setStateForBypass(State.OPEN);
+    circuitBreaker.setState(State.OPEN);
     assertEquals(circuitBreaker.getState(), "OPEN");
   }
 
   @Test
-  public void testApiResponses() {
-    var circuitBreaker = new CircuitBreaker(1, 1, 100);
-    try {
-      //Call with the paramater start_time set to huge amount of time in past so that service 
-      //replies with "Ok". Also, state is CLOSED in start
-      var serviceStartTime = System.nanoTime() - 60 * 1000 * 1000 * 1000;
-      var response = circuitBreaker.call("delayedService", serviceStartTime);
-      assertEquals(response, "Delayed service is working");
-    } catch (Exception e) {
-      System.out.println(e.getMessage());
-    }
+  public void testApiResponses() throws RemoteServiceException {
+    RemoteService mockService = new RemoteService() {
+      @Override
+      public String call() throws RemoteServiceException {
+        return "Remote Success";
+      }
+    };
+    var circuitBreaker = new DefaultCircuitBreaker(mockService, 1, 1, 100);
+    //Call with the paramater start_time set to huge amount of time in past so that service
+    //replies with "Ok". Also, state is CLOSED in start
+    var serviceStartTime = System.nanoTime() - 60 * 1000 * 1000 * 1000;
+    var response = circuitBreaker.attemptRequest();
+    assertEquals(response, "Remote Success");
+
   }
 }

circuit-breaker/src/test/java/com/iluwatar/circuitbreaker/DelayedRemoteServiceTest.java

@@ -0,0 +1,59 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.circuitbreaker;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Monitoring Service test
+ */
+public class DelayedRemoteServiceTest {
+
+  /**
+   * Testing immediate response of the delayed service.
+   *
+   * @throws RemoteServiceException
+   */
+  @Test
+  public void testDefaultConstructor() throws RemoteServiceException {
+    Assertions.assertThrows(RemoteServiceException.class, () -> {
+      var obj = new DelayedRemoteService();
+      obj.call();
+    });
+  }
+
+  /**
+   * Testing server started in past (2 seconds ago) and with a simulated delay of 1 second.
+   *
+   * @throws RemoteServiceException
+   */
+  @Test
+  public void testParameterizedConstructor() throws RemoteServiceException {
+      var obj = new DelayedRemoteService(System.nanoTime()-2000*1000*1000,1);
+      assertEquals("Delayed service is working",obj.call());
+  }
+}

circuit-breaker/src/test/java/com/iluwatar/circuitbreaker/MonitoringServiceTest.java

@@ -35,28 +35,45 @@ public class MonitoringServiceTest {
   //long timeout, int failureThreshold, long retryTimePeriod
   @Test
   public void testLocalResponse() {
-    var monitoringService = new MonitoringService();
+    var monitoringService = new MonitoringService(null,null);
     var response = monitoringService.localResourceResponse();
     assertEquals(response, "Local Service is working");
   }
 
   @Test
-  public void testRemoteResponse() {
-    var monitoringService = new MonitoringService();
-    var circuitBreaker = new CircuitBreaker(1, 1, 100);
+  public void testDelayedRemoteResponseSuccess() {
+    var delayedService = new DelayedRemoteService(System.nanoTime()-2*1000*1000*1000, 2);
+    var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000,
+        1,
+        2 * 1000 * 1000 * 1000);
+
+    var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,null);
     //Set time in past to make the server work
-    var serverStartTime = System.nanoTime() / 10;
-    var response = monitoringService.remoteResourceResponse(circuitBreaker, serverStartTime);
+    var response = monitoringService.delayedServiceResponse();
     assertEquals(response, "Delayed service is working");
   }
 
   @Test
-  public void testRemoteResponse2() {
-    var monitoringService = new MonitoringService();
-    var circuitBreaker = new CircuitBreaker(1, 1, 100);
+  public void testDelayedRemoteResponseFailure() {
+    var delayedService = new DelayedRemoteService(System.nanoTime(), 2);
+    var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000,
+        1,
+        2 * 1000 * 1000 * 1000);
+    var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,null);
     //Set time as current time as initially server fails
-    var serverStartTime = System.nanoTime();
-    var response = monitoringService.remoteResourceResponse(circuitBreaker, serverStartTime);
-    assertEquals(response, "Remote service not responding");
+    var response = monitoringService.delayedServiceResponse();
+    assertEquals(response, "Delayed service is down");
+  }
+
+  @Test
+  public void testQuickRemoteServiceResponse() {
+    var delayedService = new QuickRemoteService();
+    var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000,
+        1,
+        2 * 1000 * 1000 * 1000);
+    var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,null);
+    //Set time as current time as initially server fails
+    var response = monitoringService.delayedServiceResponse();
+    assertEquals(response, "Quick Service is working");
   }
 }

collection-pipeline/pom.xml

@@ -27,7 +27,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>collection-pipeline</artifactId>
   <dependencies>

combinator/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
 
   <artifactId>combinator</artifactId>

command/README.md

@@ -9,15 +9,20 @@ tags:
 ---
 
 ## Also known as
+
 Action, Transaction
 
 ## Intent
-Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
+
+Encapsulate a request as an object, thereby letting you parameterize clients with different
+requests, queue or log requests, and support undoable operations.
 
 ## Explanation
 Real world example
 
-> There is a wizard casting spells on a goblin. The spells are executed on the goblin one by one. The first spell shrinks the goblin and the second makes him invisible. Then the wizard reverses the spells one by one. Each spell here is a command object that can be undone.
+> There is a wizard casting spells on a goblin. The spells are executed on the goblin one by one.
+> The first spell shrinks the goblin and the second makes him invisible. Then the wizard reverses
+> the spells one by one. Each spell here is a command object that can be undone.
 
 In plain words
 
@@ -25,34 +30,32 @@ In plain words
 
 Wikipedia says
 
-> In object-oriented programming, the command pattern is a behavioral design pattern in which an object is used to encapsulate all information needed to perform an action or trigger an event at a later time.
+> In object-oriented programming, the command pattern is a behavioral design pattern in which an
+> object is used to encapsulate all information needed to perform an action or trigger an event at
+> a later time.
 
 **Programmatic Example**
 
-Here's the sample code with wizard and goblin. Let's start from the wizard class.
+Here's the sample code with wizard and goblin. Let's start from the `Wizard` class.
 
 ```java
 public class Wizard {
 
-  private static final Logger LOGGER = LoggerFactory.getLogger(Wizard.class);
-
   private final Deque<Command> undoStack = new LinkedList<>();
   private final Deque<Command> redoStack = new LinkedList<>();
 
   public Wizard() {}
 
-  public void castSpell(Command command, Target target) {
-    LOGGER.info("{} casts {} at {}", this, command, target);
-    command.execute(target);
-    undoStack.offerLast(command);
+  public void castSpell(Runnable runnable) {
+    runnable.run();
+    undoStack.offerLast(runnable);
   }
 
   public void undoLastSpell() {
     if (!undoStack.isEmpty()) {
       var previousSpell = undoStack.pollLast();
       redoStack.offerLast(previousSpell);
-      LOGGER.info("{} undoes {}", this, previousSpell);
-      previousSpell.undo();
+      previousSpell.run();
     }
   }
 
@@ -60,8 +63,7 @@ public class Wizard {
     if (!redoStack.isEmpty()) {
       var previousSpell = redoStack.pollLast();
       undoStack.offerLast(previousSpell);
-      LOGGER.info("{} redoes {}", this, previousSpell);
-      previousSpell.redo();
+      previousSpell.run();
     }
   }
 
@@ -72,84 +74,7 @@ public class Wizard {
 }
 ```
 
-Next we present the spell hierarchy.
-
-```java
-public interface Command {
-
-  void execute(Target target);
-
-  void undo();
-
-  void redo();
-
-  String toString();
-}
-
-public class InvisibilitySpell implements Command {
-
-  private Target target;
-
-  @Override
-  public void execute(Target target) {
-    target.setVisibility(Visibility.INVISIBLE);
-    this.target = target;
-  }
-
-  @Override
-  public void undo() {
-    if (target != null) {
-      target.setVisibility(Visibility.VISIBLE);
-    }
-  }
-
-  @Override
-  public void redo() {
-    if (target != null) {
-      target.setVisibility(Visibility.INVISIBLE);
-    }
-  }
-
-  @Override
-  public String toString() {
-    return "Invisibility spell";
-  }
-}
-
-public class ShrinkSpell implements Command {
-
-  private Size oldSize;
-  private Target target;
-
-  @Override
-  public void execute(Target target) {
-    oldSize = target.getSize();
-    target.setSize(Size.SMALL);
-    this.target = target;
-  }
-
-  @Override
-  public void undo() {
-    if (oldSize != null && target != null) {
-      var temp = target.getSize();
-      target.setSize(oldSize);
-      oldSize = temp;
-    }
-  }
-
-  @Override
-  public void redo() {
-    undo();
-  }
-
-  @Override
-  public String toString() {
-    return "Shrink spell";
-  }
-}
-```
-
-And last we have the goblin who's the target of the spells.
+Next, we have the goblin who's the target of the spells.
 
 ```java
 public abstract class Target {
@@ -196,47 +121,110 @@ public class Goblin extends Target {
     return "Goblin";
   }
 
+  public void changeSize() {
+    var oldSize = getSize() == Size.NORMAL ? Size.SMALL : Size.NORMAL;
+    setSize(oldSize);
+  }
+
+  public void changeVisibility() {
+    var visible = getVisibility() == Visibility.INVISIBLE
+          ? Visibility.VISIBLE : Visibility.INVISIBLE;
+    setVisibility(visible);
+  }
 }
 ```
 
-Finally here's the whole example in action.
+Finally we have the wizard in main function who casts spell
+
+```java
+public static void main(String[] args) {
+  var wizard = new Wizard();
+  var goblin = new Goblin();
+
+  // casts shrink/unshrink spell
+  wizard.castSpell(goblin::changeSize);
+
+  // casts visible/invisible spell
+  wizard.castSpell(goblin::changeVisibility);
+
+  // undo and redo casts
+   wizard.undoLastSpell();
+   wizard.redoLastSpell();
+```
+
+Here's the whole example in action.
 
 ```java
 var wizard = new Wizard();
 var goblin = new Goblin();
+
 goblin.printStatus();
-// Goblin, [size=normal] [visibility=visible]
-wizard.castSpell(new ShrinkSpell(), goblin);
-// Wizard casts Shrink spell at Goblin
+wizard.castSpell(goblin::changeSize);
 goblin.printStatus();
-// Goblin, [size=small] [visibility=visible]
-wizard.castSpell(new InvisibilitySpell(), goblin);
-// Wizard casts Invisibility spell at Goblin
+
+wizard.castSpell(goblin::changeVisibility);
 goblin.printStatus();
-// Goblin, [size=small] [visibility=invisible]
+
 wizard.undoLastSpell();
-// Wizard undoes Invisibility spell
 goblin.printStatus();
-// Goblin, [size=small] [visibility=visible]
+
+wizard.undoLastSpell();
+goblin.printStatus();
+
+wizard.redoLastSpell();
+goblin.printStatus();
+
+wizard.redoLastSpell();
+goblin.printStatus();
+```
+
+Here's the program output:
+
+```java
+Goblin, [size=normal] [visibility=visible]
+Goblin, [size=small] [visibility=visible]
+Goblin, [size=small] [visibility=invisible]
+Goblin, [size=small] [visibility=visible]
+Goblin, [size=normal] [visibility=visible]
+Goblin, [size=small] [visibility=visible]
+Goblin, [size=small] [visibility=invisible]
 ```
 
 ## Class diagram
+
 ![alt text](./etc/command.png "Command")
 
 ## Applicability
-Use the Command pattern when you want to
 
-* parameterize objects by an action to perform. You can express such parameterization in a procedural language with a callback function, that is, a function that's registered somewhere to be called at a later point. Commands are an object-oriented replacement for callbacks.
-* specify, queue, and execute requests at different times. A Command object can have a lifetime independent of the original request. If the receiver of a request can be represented in an address space-independent way, then you can transfer a command object for the request to a different process and fulfill the request there
-* support undo. The Command's execute operation can store state for reversing its effects in the command itself. The Command interface must have an added Unexecute operation that reverses the effects of a previous call to execute. Executed commands are stored in a history list. Unlimited-level undo and redo is achieved by traversing this list backwards and forwards calling unexecute and execute, respectively
-* support logging changes so that they can be reapplied in case of a system crash. By augmenting the Command interface with load and store operations, you can keep a persistent log of changes. Recovering from a crash involves reloading logged commands from disk and re-executing them with the execute operation
-* structure a system around high-level operations build on primitive operations. Such a structure is common in information systems that support transactions. A transaction encapsulates a set of changes to data. The Command pattern offers a way to model transactions. Commands have a common interface, letting you invoke all transactions the same way. The pattern also makes it easy to extend the system with new transactions
+Use the Command pattern when you want to:
+
+* Parameterize objects by an action to perform. You can express such parameterization in a
+procedural language with a callback function, that is, a function that's registered somewhere to be
+called at a later point. Commands are an object-oriented replacement for callbacks.
+* Specify, queue, and execute requests at different times. A Command object can have a lifetime
+independent of the original request. If the receiver of a request can be represented in an address
+space-independent way, then you can transfer a command object for the request to a different process
+and fulfill the request there.
+* Support undo. The Command's execute operation can store state for reversing its effects in the
+command itself. The Command interface must have an added un-execute operation that reverses the
+effects of a previous call to execute. The executed commands are stored in a history list.
+Unlimited-level undo and redo is achieved by traversing this list backwards and forwards calling
+un-execute and execute, respectively.
+* Support logging changes so that they can be reapplied in case of a system crash. By augmenting the
+Command interface with load and store operations, you can keep a persistent log of changes.
+Recovering from a crash involves reloading logged commands from disk and re-executing them with
+the execute operation.
+* Structure a system around high-level operations build on primitive operations. Such a structure is
+common in information systems that support transactions. A transaction encapsulates a set of changes
+to data. The Command pattern offers a way to model transactions. Commands have a common interface,
+letting you invoke all transactions the same way. The pattern also makes it easy to extend the
+system with new transactions.
 
 ## Typical Use Case
 
-* to keep a history of requests
-* implement callback functionality
-* implement the undo functionality
+* To keep a history of requests
+* Implement callback functionality
+* Implement the undo functionality
 
 ## Real world examples
 

command/etc/command.ucls

@@ -1,116 +1,89 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true" 
-  realizations="true" associations="true" dependencies="false" nesting-relationships="true">  
-  <class id="1" language="java" name="com.iluwatar.command.ShrinkSpell" project="command" 
-    file="/command/src/main/java/com/iluwatar/command/ShrinkSpell.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="178" width="141" x="-30" y="681"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <class id="2" language="java" name="com.iluwatar.command.Goblin" project="command" 
-    file="/command/src/main/java/com/iluwatar/command/Goblin.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="129" y="1223"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <class id="3" language="java" name="com.iluwatar.command.Wizard" project="command" 
-    file="/command/src/main/java/com/iluwatar/command/Wizard.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="129" y="362"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <class id="4" language="java" name="com.iluwatar.command.Command" project="command" 
-    file="/command/src/main/java/com/iluwatar/command/Command.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="129" y="561"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <class id="5" language="java" name="com.iluwatar.command.InvisibilitySpell" project="command" 
-    file="/command/src/main/java/com/iluwatar/command/InvisibilitySpell.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="160" width="141" x="151" y="681"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <class id="6" language="java" name="com.iluwatar.command.Target" project="command" 
-    file="/command/src/main/java/com/iluwatar/command/Target.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="129" y="1014"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <association id="7">    
-    <end type="SOURCE" refId="3" navigable="false">      
-      <attribute id="8" name="redoStack">        
-        <position height="20" width="67" x="140" y="451"/>      
-      </attribute>      
-      <multiplicity id="9" minimum="0" maximum="2147483647">        
-        <position height="18" width="25" x="221" y="452"/>      
-      </multiplicity>    
-    </end>    
-    <end type="TARGET" refId="4" navigable="true"/>    
-    <display labels="true" multiplicity="true"/>  
-  </association>  
-  <generalization id="10">    
-    <end type="SOURCE" refId="2"/>    
-    <end type="TARGET" refId="6"/>  
-  </generalization>  
-  <association id="11">    
-    <end type="SOURCE" refId="1" navigable="false">      
-      <attribute id="12" name="target"/>      
-      <multiplicity id="13" minimum="0" maximum="1"/>    
-    </end>    
-    <end type="TARGET" refId="6" navigable="true"/>    
-    <display labels="true" multiplicity="true"/>  
-  </association>  
-  <generalization id="14">    
-    <end type="SOURCE" refId="1"/>    
-    <end type="TARGET" refId="4"/>  
-  </generalization>  
-  <association id="15">    
-    <end type="SOURCE" refId="3" navigable="false">      
-      <attribute id="16" name="undoStack">        
-        <position height="20" width="70" x="-17" y="451"/>      
-      </attribute>      
-      <multiplicity id="17" minimum="0" maximum="2147483647">        
-        <position height="18" width="25" x="60" y="452"/>      
-      </multiplicity>    
-    </end>    
-    <end type="TARGET" refId="4" navigable="true"/>    
-    <display labels="true" multiplicity="true"/>  
-  </association>  
-  <generalization id="18">    
-    <end type="SOURCE" refId="5"/>    
-    <end type="TARGET" refId="4"/>  
-  </generalization>  
-  <association id="19">    
-    <end type="SOURCE" refId="5" navigable="false">      
-      <attribute id="20" name="target"/>      
-      <multiplicity id="21" minimum="0" maximum="1"/>    
-    </end>    
-    <end type="TARGET" refId="6" navigable="true"/>    
-    <display labels="true" multiplicity="true"/>  
-  </association>  
-  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-    sort-features="false" accessors="true" visibility="true">    
-    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
-    <operations public="true" package="true" protected="true" private="true" static="true"/>  
-  </classifier-display>  
+<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
+  realizations="true" associations="true" dependencies="false" nesting-relationships="true">
+  <class id="2" language="java" name="com.iluwatar.command.Goblin" project="command"
+    file="/command/src/main/java/com/iluwatar/command/Goblin.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="-1" width="-1" x="129" y="1223"/>
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
+      sort-features="false" accessors="true" visibility="true">
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>
+      <operations public="true" package="true" protected="true" private="true" static="true"/>
+    </display>
+  </class>
+  <class id="3" language="java" name="com.iluwatar.command.Wizard" project="command"
+    file="/command/src/main/java/com/iluwatar/command/Wizard.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="-1" width="-1" x="129" y="362"/>
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
+      sort-features="false" accessors="true" visibility="true">
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>
+      <operations public="true" package="true" protected="true" private="true" static="true"/>
+    </display>
+  </class>
+  <class id="6" language="java" name="com.iluwatar.command.Target" project="command"
+    file="/command/src/main/java/com/iluwatar/command/Target.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="-1" width="-1" x="129" y="1014"/>
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
+      sort-features="false" accessors="true" visibility="true">
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>
+      <operations public="true" package="true" protected="true" private="true" static="true"/>
+    </display>
+  </class>
+  <association id="7">
+    <end type="SOURCE" refId="3" navigable="false">
+      <attribute id="8" name="redoStack">
+        <position height="20" width="67" x="140" y="451"/>
+      </attribute>
+      <multiplicity id="9" minimum="0" maximum="2147483647">
+        <position height="18" width="25" x="221" y="452"/>
+      </multiplicity>
+    </end>
+    <end type="TARGET" refId="4" navigable="true"/>
+    <display labels="true" multiplicity="true"/>
+  </association>
+  <generalization id="10">
+    <end type="SOURCE" refId="2"/>
+    <end type="TARGET" refId="6"/>
+  </generalization>
+  <association id="11">
+    <end type="SOURCE" refId="1" navigable="false">
+      <attribute id="12" name="target"/>
+      <multiplicity id="13" minimum="0" maximum="1"/>
+    </end>
+    <end type="TARGET" refId="6" navigable="true"/>
+    <display labels="true" multiplicity="true"/>
+  </association>
+  <generalization id="14">
+    <end type="SOURCE" refId="1"/>
+    <end type="TARGET" refId="4"/>
+  </generalization>
+  <association id="15">
+    <end type="SOURCE" refId="3" navigable="false">
+      <attribute id="16" name="undoStack">
+        <position height="20" width="70" x="-17" y="451"/>
+      </attribute>
+      <multiplicity id="17" minimum="0" maximum="2147483647">
+        <position height="18" width="25" x="60" y="452"/>
+      </multiplicity>
+    </end>
+    <end type="TARGET" refId="4" navigable="true"/>
+    <display labels="true" multiplicity="true"/>
+  </association>
+  <generalization id="18">
+    <end type="SOURCE" refId="5"/>
+    <end type="TARGET" refId="4"/>
+  </generalization>
+  <association id="19">
+    <end type="SOURCE" refId="5" navigable="false">
+      <attribute id="20" name="target"/>
+      <multiplicity id="21" minimum="0" maximum="1"/>
+    </end>
+    <end type="TARGET" refId="6" navigable="true"/>
+    <display labels="true" multiplicity="true"/>
+  </association>
+  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
+    sort-features="false" accessors="true" visibility="true">
+    <attributes public="true" package="true" protected="true" private="true" static="true"/>
+    <operations public="true" package="true" protected="true" private="true" static="true"/>
+  </classifier-display>
   <association-display labels="true" multiplicity="true"/>
-</class-diagram>
+</class-diagram>

command/etc/command.urm.puml

@@ -4,33 +4,11 @@ package com.iluwatar.command {
     + App()
     + main(args : String[]) {static}
   }
-  interface Command {
-    + Command()
-    + execute(Target) {abstract}
-    + redo() {abstract}
-    + toString() : String {abstract}
-    + undo() {abstract}
-  }
   class Goblin {
     + Goblin()
     + toString() : String
-  }
-  class InvisibilitySpell {
-    - target : Target
-    + InvisibilitySpell()
-    + execute(target : Target)
-    + redo()
-    + toString() : String
-    + undo()
-  }
-  class ShrinkSpell {
-    - oldSize : Size
-    - target : Target
-    + ShrinkSpell()
-    + execute(target : Target)
-    + redo()
-    + toString() : String
-    + undo()
+    + changeSize()
+    + changeVisibility()
   }
   enum Size {
     + NORMAL {static}
@@ -62,22 +40,19 @@ package com.iluwatar.command {
   }
   class Wizard {
     - LOGGER : Logger {static}
-    - redoStack : Deque<Command>
-    - undoStack : Deque<Command>
+    - redoStack : Deque<Runnable>
+    - undoStack : Deque<Runnable>
     + Wizard()
-    + castSpell(command : Command, target : Target)
+    + castSpell(Runnable : runnable)
     + redoLastSpell()
     + toString() : String
     + undoLastSpell()
   }
 }
 Target -->  "-size" Size
-Wizard -->  "-undoStack" Command
-ShrinkSpell -->  "-oldSize" Size
-InvisibilitySpell -->  "-target" Target
-ShrinkSpell -->  "-target" Target
+Wizard -->  "-changeSize" Goblin
+Wizard -->  "-changeVisibility" Goblin
 Target -->  "-visibility" Visibility
 Goblin --|> Target
-InvisibilitySpell ..|> Command
-ShrinkSpell ..|> Command
+App --> "castSpell" Wizard
 @enduml

command/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>command</artifactId>
   <dependencies>

command/src/main/java/com/iluwatar/command/App.java

@@ -30,12 +30,10 @@ package com.iluwatar.command;
  *
  * <p>Four terms always associated with the command pattern are command, receiver, invoker and
  * client. A command object (spell) knows about the receiver (target) and invokes a method of the
- * receiver. Values for parameters of the receiver method are stored in the command. The receiver
- * then does the work. An invoker object (wizard) knows how to execute a command, and optionally
- * does bookkeeping about the command execution. The invoker does not know anything about a concrete
- * command, it knows only about command interface. Both an invoker object and several command
- * objects are held by a client object (app). The client decides which commands to execute at which
- * points. To execute a command, it passes the command object to the invoker object.
+ * receiver. An invoker object (wizard) receives a reference to the command to be executed and
+ * optionally does bookkeeping about the command execution. The invoker does not know anything
+ * about how the command is executed. The client decides which commands to execute at which
+ * points. To execute a command, it passes a reference of the function to the invoker object.
  *
  * <p>In other words, in this example the wizard casts spells on the goblin. The wizard keeps track
  * of the previous spells cast, so it is easy to undo them. In addition, the wizard keeps track of
@@ -54,10 +52,10 @@ public class App {
 
     goblin.printStatus();
 
-    wizard.castSpell(new ShrinkSpell(), goblin);
+    wizard.castSpell(goblin::changeSize);
     goblin.printStatus();
 
-    wizard.castSpell(new InvisibilitySpell(), goblin);
+    wizard.castSpell(goblin::changeVisibility);
     goblin.printStatus();
 
     wizard.undoLastSpell();

command/src/main/java/com/iluwatar/command/Goblin.java

@@ -37,5 +37,4 @@ public class Goblin extends Target {
   public String toString() {
     return "Goblin";
   }
-
 }

command/src/main/java/com/iluwatar/command/Target.java

@@ -62,4 +62,21 @@ public abstract class Target {
   public void printStatus() {
     LOGGER.info("{}, [size={}] [visibility={}]", this, getSize(), getVisibility());
   }
+
+  /**
+   * Changes the size of the target.
+   */
+  public void changeSize() {
+    var oldSize = getSize() == Size.NORMAL ? Size.SMALL : Size.NORMAL;
+    setSize(oldSize);
+  }
+
+  /**
+   * Changes the visibility of the target.
+   */
+  public void changeVisibility() {
+    var visible = getVisibility() == Visibility.INVISIBLE
+            ? Visibility.VISIBLE : Visibility.INVISIBLE;
+    setVisibility(visible);
+  }
 }

command/src/main/java/com/iluwatar/command/Wizard.java

@@ -25,30 +25,24 @@ package com.iluwatar.command;
 
 import java.util.Deque;
 import java.util.LinkedList;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 /**
  * Wizard is the invoker of the commands.
  */
 public class Wizard {
 
-  private static final Logger LOGGER = LoggerFactory.getLogger(Wizard.class);
-
-  private final Deque<Command> undoStack = new LinkedList<>();
-  private final Deque<Command> redoStack = new LinkedList<>();
+  private final Deque<Runnable> undoStack = new LinkedList<>();
+  private final Deque<Runnable> redoStack = new LinkedList<>();
 
   public Wizard() {
-    // comment to ignore sonar issue: LEVEL critical
   }
 
   /**
    * Cast spell.
    */
-  public void castSpell(Command command, Target target) {
-    LOGGER.info("{} casts {} at {}", this, command, target);
-    command.execute(target);
-    undoStack.offerLast(command);
+  public void castSpell(Runnable runnable) {
+    runnable.run();
+    undoStack.offerLast(runnable);
   }
 
   /**
@@ -58,8 +52,7 @@ public class Wizard {
     if (!undoStack.isEmpty()) {
       var previousSpell = undoStack.pollLast();
       redoStack.offerLast(previousSpell);
-      LOGGER.info("{} undoes {}", this, previousSpell);
-      previousSpell.undo();
+      previousSpell.run();
     }
   }
 
@@ -70,8 +63,7 @@ public class Wizard {
     if (!redoStack.isEmpty()) {
       var previousSpell = redoStack.pollLast();
       undoStack.offerLast(previousSpell);
-      LOGGER.info("{} redoes {}", this, previousSpell);
-      previousSpell.redo();
+      previousSpell.run();
     }
   }
 

command/src/test/java/com/iluwatar/command/CommandTest.java

@@ -56,10 +56,10 @@ public class CommandTest {
     var wizard = new Wizard();
     var goblin = new Goblin();
 
-    wizard.castSpell(new ShrinkSpell(), goblin);
+    wizard.castSpell(goblin::changeSize);
     verifyGoblin(goblin, GOBLIN, Size.SMALL, Visibility.VISIBLE);
 
-    wizard.castSpell(new InvisibilitySpell(), goblin);
+    wizard.castSpell(goblin::changeVisibility);
     verifyGoblin(goblin, GOBLIN, Size.SMALL, Visibility.INVISIBLE);
 
     wizard.undoLastSpell();

commander/pom.xml

@@ -27,7 +27,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>commander</artifactId>
   <dependencies>

composite/README.md

@@ -9,15 +9,17 @@ tags:
 ---
 
 ## Intent
-Compose objects into tree structures to represent part-whole
-hierarchies. Composite lets clients treat individual objects and compositions
-of objects uniformly.
+
+Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients 
+treat individual objects and compositions of objects uniformly.
 
 ## Explanation
 
 Real world example
 
-> Every sentence is composed of words which are in turn composed of characters. Each of these objects is printable and they can have something printed before or after them like sentence always ends with full stop and word always has space before it
+> Every sentence is composed of words which are in turn composed of characters. Each of these 
+> objects is printable and they can have something printed before or after them like sentence always 
+> ends with full stop and word always has space before it.
 
 In plain words
 
@@ -25,11 +27,16 @@ In plain words
 
 Wikipedia says
 
-> In software engineering, the composite pattern is a partitioning design pattern. The composite pattern describes that a group of objects is to be treated in the same way as a single instance of an object. The intent of a composite is to "compose" objects into tree structures to represent part-whole hierarchies. Implementing the composite pattern lets clients treat individual objects and compositions uniformly.
+> In software engineering, the composite pattern is a partitioning design pattern. The composite 
+> pattern describes that a group of objects is to be treated in the same way as a single instance of 
+> an object. The intent of a composite is to "compose" objects into tree structures to represent 
+> part-whole hierarchies. Implementing the composite pattern lets clients treat individual objects 
+> and compositions uniformly.
 
 **Programmatic Example**
 
-Taking our sentence example from above. Here we have the base class and different printable types
+Taking our sentence example from above. Here we have the base class `LetterComposite` and the 
+different printable types `Letter`, `Word` and `Sentence`. 
 
 ```java
 public abstract class LetterComposite {
@@ -102,7 +109,7 @@ public class Sentence extends LetterComposite {
 }
 ```
 
-Then we have a messenger to carry messages
+Then we have a messenger to carry messages:
 
 ```java
 public class Messenger {
@@ -143,7 +150,7 @@ public class Messenger {
 }
 ```
 
-And then it can be used as
+And then it can be used as:
 
 ```java
 var orcMessage = new Messenger().messageFromOrcs();
@@ -153,13 +160,16 @@ elfMessage.print(); // Much wind pours from your mouth.
 ```
 
 ## Class diagram
+
 ![alt text](./etc/composite.urm.png "Composite class diagram")
 
 ## Applicability
+
 Use the Composite pattern when
 
-* you want to represent part-whole hierarchies of objects
-* you want clients to be able to ignore the difference between compositions of objects and individual objects. Clients will treat all objects in the composite structure uniformly
+* You want to represent part-whole hierarchies of objects.
+* You want clients to be able to ignore the difference between compositions of objects and 
+individual objects. Clients will treat all objects in the composite structure uniformly.
 
 ## Real world examples
 

composite/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>composite</artifactId>
   <dependencies>

converter/README.md

@@ -9,16 +9,19 @@ tags:
 ---
 
 ## Intent
-The purpose of the Converter Pattern is to provide a generic, common way of bidirectional
+
+The purpose of the Converter pattern is to provide a generic, common way of bidirectional
 conversion between corresponding types, allowing a clean implementation in which the types do not
-need to be aware of each other. Moreover, the Converter Pattern introduces bidirectional collection
+need to be aware of each other. Moreover, the Converter pattern introduces bidirectional collection
 mapping, reducing a boilerplate code to minimum.
 
 ## Explanation
 
 Real world example
 
-> In real world applications it is often the case that database layer consists of entities that need to be mapped into DTOs for use on the business logic layer. Similar mapping is done for potentially huge amount of classes and we need a generic way to achieve this.
+> In real world applications it is often the case that database layer consists of entities that need 
+> to be mapped into DTOs for use on the business logic layer. Similar mapping is done for 
+> potentially huge amount of classes and we need a generic way to achieve this.
 
 In plain words
 
@@ -26,7 +29,8 @@ In plain words
 
 **Programmatic Example**
 
-We need a generic solution for the mapping problem. To achieve this, let's introduce a generic converter.
+We need a generic solution for the mapping problem. To achieve this, let's introduce a generic 
+converter.
 
 ```java
 public class Converter<T, U> {
@@ -77,7 +81,7 @@ public class UserConverter extends Converter<UserDto, User> {
 }
 ```
 
-Now mapping between User and UserDto becomes trivial.
+Now mapping between `User` and `UserDto` becomes trivial.
 
 ```java
 var userConverter = new UserConverter();
@@ -86,14 +90,18 @@ var user = userConverter.convertFromDto(dtoUser);
 ```
 
 ## Class diagram
+
 ![alt text](./etc/converter.png "Converter Pattern")
 
 ## Applicability
+
 Use the Converter Pattern in the following situations:
 
-* When you have types that logically correspond which other and you need to convert entities between them
-* When you want to provide different ways of types conversions depending on a context
-* Whenever you introduce a DTO (Data transfer object), you will probably need to convert it into the domain equivalence
+* When you have types that logically correspond with each other and you need to convert entities 
+between them.
+* When you want to provide different ways of types conversions depending on the context.
+* Whenever you introduce a DTO (Data transfer object), you will probably need to convert it into the 
+domain equivalence.
 
 ## Credits
 

converter/pom.xml

@@ -20,7 +20,7 @@
 	<parent>
 		<artifactId>java-design-patterns</artifactId>
 		<groupId>com.iluwatar</groupId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>converter</artifactId>
 	<modelVersion>4.0.0</modelVersion>

cqrs/pom.xml

@@ -30,7 +30,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>cqrs</artifactId>
 	<dependencies>

dao/README.md

@@ -9,13 +9,15 @@ tags:
 ---
 
 ## Intent
+
 Object provides an abstract interface to some type of database or other persistence mechanism.
 
 ## Explanation
 
 Real world example
 
-> There's a set of customers that need to be persisted to database. Additionally we need the whole set of CRUD (create/read/update/delete) operations so we can operate on customers easily. 
+> There's a set of customers that need to be persisted to database. Additionally we need the whole 
+> set of CRUD (create/read/update/delete) operations so we can operate on customers easily. 
 
 In plain words
 
@@ -23,11 +25,12 @@ In plain words
 
 Wikipedia says
 
-> In computer software, a data access object (DAO) is a pattern that provides an abstract interface to some type of database or other persistence mechanism.
+> In computer software, a data access object (DAO) is a pattern that provides an abstract interface 
+> to some type of database or other persistence mechanism.
 
 **Programmatic Example**
 
-Walking through our customers example, here's the basic Customer entity.
+Walking through our customers example, here's the basic `Customer` entity.
 
 ```java
 public class Customer {
@@ -41,60 +44,13 @@ public class Customer {
     this.firstName = firstName;
     this.lastName = lastName;
   }
-
-  public int getId() {
-    return id;
-  }
-
-  public void setId(final int id) {
-    this.id = id;
-  }
-
-  public String getFirstName() {
-    return firstName;
-  }
-
-  public void setFirstName(final String firstName) {
-    this.firstName = firstName;
-  }
-
-  public String getLastName() {
-    return lastName;
-  }
-
-  public void setLastName(final String lastName) {
-    this.lastName = lastName;
-  }
-
-  @Override
-  public String toString() {
-    return "Customer{" + "id=" + getId() + ", firstName='" + getFirstName() + '\'' + ", lastName='"
-        + getLastName() + '\'' + '}';
-  }
-
-  @Override
-  public boolean equals(final Object that) {
-    var isEqual = false;
-    if (this == that) {
-      isEqual = true;
-    } else if (that != null && getClass() == that.getClass()) {
-      final var customer = (Customer) that;
-      if (getId() == customer.getId()) {
-        isEqual = true;
-      }
-    }
-    return isEqual;
-  }
-
-  @Override
-  public int hashCode() {
-    return getId();
-  }
+  // getters and setters ->
+  ...
 }
 ```
 
-Here's the DAO interface and two different implementations for it. InMemoryCustomerDao keeps a simple map of customers 
-in memory while DBCustomerDao is the real RDBMS implementation.
+Here's the `CustomerDao` interface and two different implementations for it. `InMemoryCustomerDao` 
+keeps a simple map of customers in memory while `DBCustomerDao` is the real RDBMS implementation.
 
 ```java
 public interface CustomerDao {
@@ -114,35 +70,8 @@ public class InMemoryCustomerDao implements CustomerDao {
 
   private final Map<Integer, Customer> idToCustomer = new HashMap<>();
 
-  @Override
-  public Stream<Customer> getAll() {
-    return idToCustomer.values().stream();
-  }
-
-  @Override
-  public Optional<Customer> getById(final int id) {
-    return Optional.ofNullable(idToCustomer.get(id));
-  }
-
-  @Override
-  public boolean add(final Customer customer) {
-    if (getById(customer.getId()).isPresent()) {
-      return false;
-    }
-
-    idToCustomer.put(customer.getId(), customer);
-    return true;
-  }
-
-  @Override
-  public boolean update(final Customer customer) {
-    return idToCustomer.replace(customer.getId(), customer) != null;
-  }
-
-  @Override
-  public boolean delete(final Customer customer) {
-    return idToCustomer.remove(customer.getId()) != null;
-  }
+  // implement the interface using the map
+  ...
 }
 
 public class DbCustomerDao implements CustomerDao {
@@ -155,121 +84,8 @@ public class DbCustomerDao implements CustomerDao {
     this.dataSource = dataSource;
   }
 
-  @Override
-  public Stream<Customer> getAll() throws Exception {
-    try {
-      var connection = getConnection();
-      var statement = connection.prepareStatement("SELECT * FROM CUSTOMERS");
-      var resultSet = statement.executeQuery();
-      return StreamSupport.stream(new Spliterators.AbstractSpliterator<Customer>(Long.MAX_VALUE,
-          Spliterator.ORDERED) {
-
-        @Override
-        public boolean tryAdvance(Consumer<? super Customer> action) {
-          try {
-            if (!resultSet.next()) {
-              return false;
-            }
-            action.accept(createCustomer(resultSet));
-            return true;
-          } catch (SQLException e) {
-            throw new RuntimeException(e);
-          }
-        }
-      }, false).onClose(() -> mutedClose(connection, statement, resultSet));
-    } catch (SQLException e) {
-      throw new CustomException(e.getMessage(), e);
-    }
-  }
-
-  private Connection getConnection() throws SQLException {
-    return dataSource.getConnection();
-  }
-
-  private void mutedClose(Connection connection, PreparedStatement statement, ResultSet resultSet) {
-    try {
-      resultSet.close();
-      statement.close();
-      connection.close();
-    } catch (SQLException e) {
-      LOGGER.info("Exception thrown " + e.getMessage());
-    }
-  }
-
-  private Customer createCustomer(ResultSet resultSet) throws SQLException {
-    return new Customer(resultSet.getInt("ID"),
-        resultSet.getString("FNAME"),
-        resultSet.getString("LNAME"));
-  }
-
-  @Override
-  public Optional<Customer> getById(int id) throws Exception {
-
-    ResultSet resultSet = null;
-
-    try (var connection = getConnection();
-         var statement = connection.prepareStatement("SELECT * FROM CUSTOMERS WHERE ID = ?")) {
-
-      statement.setInt(1, id);
-      resultSet = statement.executeQuery();
-      if (resultSet.next()) {
-        return Optional.of(createCustomer(resultSet));
-      } else {
-        return Optional.empty();
-      }
-    } catch (SQLException ex) {
-      throw new CustomException(ex.getMessage(), ex);
-    } finally {
-      if (resultSet != null) {
-        resultSet.close();
-      }
-    }
-  }
-
-  @Override
-  public boolean add(Customer customer) throws Exception {
-    if (getById(customer.getId()).isPresent()) {
-      return false;
-    }
-
-    try (var connection = getConnection();
-         var statement = connection.prepareStatement("INSERT INTO CUSTOMERS VALUES (?,?,?)")) {
-      statement.setInt(1, customer.getId());
-      statement.setString(2, customer.getFirstName());
-      statement.setString(3, customer.getLastName());
-      statement.execute();
-      return true;
-    } catch (SQLException ex) {
-      throw new CustomException(ex.getMessage(), ex);
-    }
-  }
-
-  @Override
-  public boolean update(Customer customer) throws Exception {
-    try (var connection = getConnection();
-         var statement =
-             connection
-                 .prepareStatement("UPDATE CUSTOMERS SET FNAME = ?, LNAME = ? WHERE ID = ?")) {
-      statement.setString(1, customer.getFirstName());
-      statement.setString(2, customer.getLastName());
-      statement.setInt(3, customer.getId());
-      return statement.executeUpdate() > 0;
-    } catch (SQLException ex) {
-      throw new CustomException(ex.getMessage(), ex);
-    }
-  }
-
-  @Override
-  public boolean delete(Customer customer) throws Exception {
-    try (var connection = getConnection();
-         var statement = connection.prepareStatement("DELETE FROM CUSTOMERS WHERE ID = ?")) {
-      statement.setInt(1, customer.getId());
-      return statement.executeUpdate() > 0;
-    } catch (SQLException ex) {
-      throw new CustomException(ex.getMessage(), ex);
-    }
-  }
-}
+  // implement the interface using the data source
+  ...
 ```
 
 Finally here's how we use our DAO to manage customers.
@@ -301,15 +117,45 @@ Finally here's how we use our DAO to manage customers.
     deleteSchema(dataSource);
 ```
 
+The program output:
+
+```java
+customerDao.getAllCustomers(): 
+Customer{id=1, firstName='Adam', lastName='Adamson'}
+Customer{id=2, firstName='Bob', lastName='Bobson'}
+Customer{id=3, firstName='Carl', lastName='Carlson'}
+customerDao.getCustomerById(2): Optional[Customer{id=2, firstName='Bob', lastName='Bobson'}]
+customerDao.getAllCustomers(): java.util.stream.ReferencePipeline$Head@7cef4e59
+customerDao.getAllCustomers(): 
+Customer{id=1, firstName='Adam', lastName='Adamson'}
+Customer{id=2, firstName='Bob', lastName='Bobson'}
+Customer{id=3, firstName='Carl', lastName='Carlson'}
+Customer{id=4, firstName='Daniel', lastName='Danielson'}
+customerDao.getAllCustomers(): java.util.stream.ReferencePipeline$Head@2db0f6b2
+customerDao.getAllCustomers(): 
+Customer{id=1, firstName='Adam', lastName='Adamson'}
+Customer{id=2, firstName='Bob', lastName='Bobson'}
+Customer{id=3, firstName='Carl', lastName='Carlson'}
+customerDao.getCustomerById(2): Optional[Customer{id=2, firstName='Bob', lastName='Bobson'}]
+customerDao.getAllCustomers(): java.util.stream.ReferencePipeline$Head@12c8a2c0
+customerDao.getAllCustomers(): 
+Customer{id=1, firstName='Adam', lastName='Adamson'}
+Customer{id=2, firstName='Bob', lastName='Bobson'}
+Customer{id=3, firstName='Carl', lastName='Carlson'}
+Customer{id=4, firstName='Daniel', lastName='Danielson'}
+customerDao.getAllCustomers(): java.util.stream.ReferencePipeline$Head@6ec8211c
+```
 
 ## Class diagram
+
 ![alt text](./etc/dao.png "Data Access Object")
 
 ## Applicability
-Use the Data Access Object in any of the following situations
 
-* when you want to consolidate how the data layer is accessed
-* when you want to avoid writing multiple data retrieval/persistence layers
+Use the Data Access Object in any of the following situations:
+
+* When you want to consolidate how the data layer is accessed.
+* When you want to avoid writing multiple data retrieval/persistence layers.
 
 ## Credits
 

dao/pom.xml

@@ -30,7 +30,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>dao</artifactId>
 

data-bus/pom.xml

@@ -33,7 +33,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.23.0-SNAPSHOT</version>
+        <version>1.24.0-SNAPSHOT</version>
     </parent>
     <artifactId>data-bus</artifactId>
     <dependencies>

data-locality/pom.xml

@@ -30,7 +30,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>data-locality</artifactId>
 

data-mapper/pom.xml

@@ -28,7 +28,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.23.0-SNAPSHOT</version>
+		<version>1.24.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>data-mapper</artifactId>
 	<dependencies>

data-transfer-object/README.md

@@ -9,13 +9,16 @@ tags:
 ---
 
 ## Intent
-Pass data with multiple attributes in one shot from client to server, to avoid multiple calls to remote server. 
+
+Pass data with multiple attributes in one shot from client to server, to avoid multiple calls to 
+remote server. 
 
 ## Explanation
 
 Real world example
 
-> We need to fetch information about customers from remote database. Instead of querying the attributes one at a time, we use DTOs to transfer all the relevant attributes in a single shot.     
+> We need to fetch information about customers from remote database. Instead of querying the 
+> attributes one at a time, we use DTOs to transfer all the relevant attributes in a single shot.     
 
 In plain words
 
@@ -23,16 +26,17 @@ In plain words
 
 Wikipedia says
 
-> In the field of programming a data transfer object (DTO) is an object that carries data between processes. The 
-motivation for its use is that communication between processes is usually done resorting to remote interfaces 
-(e.g., web services), where each call is an expensive operation. Because the majority of the cost of each call is 
-related to the round-trip time between the client and the server, one way of reducing the number of calls is to use an 
-object (the DTO) that aggregates the data that would have been transferred by the several calls, but that is served by 
-one call only.
+> In the field of programming a data transfer object (DTO) is an object that carries data between 
+> processes. The motivation for its use is that communication between processes is usually done 
+> resorting to remote interfaces (e.g. web services), where each call is an expensive operation. 
+> Because the majority of the cost of each call is related to the round-trip time between the client 
+> and the server, one way of reducing the number of calls is to use an object (the DTO) that 
+> aggregates the data that would have been transferred by the several calls, but that is served by 
+> one call only.
 
 **Programmatic Example**
 
-Let's first introduce our simple customer DTO class.
+Let's first introduce our simple `CustomerDTO` class.
 
 ```java
 public class CustomerDto {
@@ -60,7 +64,7 @@ public class CustomerDto {
 }
 ```
 
-Customer resource class acts as the server for customer information.
+`CustomerResource` class acts as the server for customer information.
 
 ```java
 public class CustomerResource {
@@ -94,10 +98,12 @@ Now fetching customer information is easy since we have the DTOs.
 ```
 
 ## Class diagram
+
 ![alt text](./etc/data-transfer-object.urm.png "data-transfer-object")
 
 ## Applicability
-Use the Data Transfer Object pattern when
+
+Use the Data Transfer Object pattern when:
 
 * The client is asking for multiple information. And the information is related.
 * When you want to boost the performance to get resources.

data-transfer-object/pom.xml

@@ -28,7 +28,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.23.0-SNAPSHOT</version>
+        <version>1.24.0-SNAPSHOT</version>
     </parent>
     <artifactId>data-transfer-object</artifactId>
     <dependencies>

data-transfer-object/src/main/java/com/iluwatar/datatransfer/App.java

@@ -23,7 +23,13 @@
 
 package com.iluwatar.datatransfer;
 
+import com.iluwatar.datatransfer.customer.CustomerDto;
+import com.iluwatar.datatransfer.customer.CustomerResource;
+import com.iluwatar.datatransfer.product.Product;
+import com.iluwatar.datatransfer.product.ProductDto;
+import com.iluwatar.datatransfer.product.ProductResource;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -32,11 +38,17 @@ import org.slf4j.LoggerFactory;
  * The Data Transfer Object pattern is a design pattern in which an data transfer object is used to
  * serve related information together to avoid multiple call for each piece of information.
  *
- * <p>In this example, ({@link App}) as as customer details consumer i.e. client to
- * request for customer details to server.
+ * <p>In the first example, {@link App} is a customer details consumer i.e. client to
+ * request for customer details to server. {@link CustomerResource} act as server to serve customer
+ * information. {@link CustomerDto} is data transfer object to share customer information.
+ *
+ * <p>In the second example, {@link App} is a product details consumer i.e. client to
+ * request for product details to server. {@link ProductResource} acts as server to serve
+ * product information. {@link ProductDto} is data transfer object to share product information.
+ *
+ * <p>The pattern implementation is a bit different in each of the examples. The first can be
+ * thought as a traditional example and the second is an enum based implementation.
  *
- * <p>CustomerResource ({@link CustomerResource}) act as server to serve customer information. And
- * The CustomerDto ({@link CustomerDto} is data transfer object to share customer information.
  */
 public class App {
 
@@ -48,6 +60,8 @@ public class App {
    * @param args program argument.
    */
   public static void main(String[] args) {
+
+    // Example 1: Customer DTO
     var customerOne = new CustomerDto("1", "Kelly", "Brown");
     var customerTwo = new CustomerDto("2", "Alfonso", "Bass");
     var customers = new ArrayList<>(List.of(customerOne, customerTwo));
@@ -72,6 +86,53 @@ public class App {
     customerResource.save(customerThree);
     allCustomers = customerResource.getAllCustomers();
     printCustomerDetails(allCustomers);
+
+    // Example 2: Product DTO
+    Product tv =
+        new Product().setId(1L).setName("TV").setSupplier("Sony").setPrice(1000D).setCost(1090D);
+    Product microwave =
+        new Product()
+            .setId(2L)
+            .setName("microwave")
+            .setSupplier("Delonghi")
+            .setPrice(1000D)
+            .setCost(1090D);
+    Product refrigerator =
+        new Product()
+            .setId(3L)
+            .setName("refrigerator")
+            .setSupplier("Botsch")
+            .setPrice(1000D)
+            .setCost(1090D);
+    Product airConditioner =
+        new Product()
+            .setId(4L)
+            .setName("airConditioner")
+            .setSupplier("LG")
+            .setPrice(1000D)
+            .setCost(1090D);
+    List<Product> products =
+        new ArrayList<>(Arrays.asList(tv, microwave, refrigerator, airConditioner));
+    ProductResource productResource = new ProductResource(products);
+
+    LOGGER.info(
+        "####### List of products including sensitive data just for admins: \n {}",
+        Arrays.toString(productResource.getAllProductsForAdmin().toArray()));
+    LOGGER.info(
+        "####### List of products for customers: \n {}",
+        Arrays.toString(productResource.getAllProductsForCustomer().toArray()));
+
+    LOGGER.info("####### Going to save Sony PS5 ...");
+    ProductDto.Request.Create createProductRequestDto =
+        new ProductDto.Request.Create()
+            .setName("PS5")
+            .setCost(1000D)
+            .setPrice(1220D)
+            .setSupplier("Sony");
+    productResource.save(createProductRequestDto);
+    LOGGER.info(
+        "####### List of products after adding PS5: {}",
+        Arrays.toString(productResource.getProducts().toArray()));
   }
 
   private static void printCustomerDetails(List<CustomerDto> allCustomers) {

data-transfer-object/src/main/java/com/iluwatar/datatransfer/customer/CustomerDto.java

@@ -21,7 +21,7 @@
  * THE SOFTWARE.
  */
 
-package com.iluwatar.datatransfer;
+package com.iluwatar.datatransfer.customer;
 
 /**
  * {@link CustomerDto} is a data transfer object POJO. Instead of sending individual information to

data-transfer-object/src/main/java/com/iluwatar/datatransfer/customer/CustomerResource.java

@@ -21,7 +21,7 @@
  * THE SOFTWARE.
  */
 
-package com.iluwatar.datatransfer;
+package com.iluwatar.datatransfer.customer;
 
 import java.util.List;
 

data-transfer-object/src/main/java/com/iluwatar/datatransfer/product/Product.java

@@ -0,0 +1,114 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.datatransfer.product;
+
+/**
+ * {@link Product} is a entity class for product entity. This class act as entity in the demo.
+ */
+public final class Product {
+  private Long id;
+  private String name;
+  private Double price;
+  private Double cost;
+  private String supplier;
+
+  /**
+   * Constructor.
+   *
+   * @param id       product id
+   * @param name     product name
+   * @param price    product price
+   * @param cost     product cost
+   * @param supplier product supplier
+   */
+  public Product(Long id, String name, Double price, Double cost, String supplier) {
+    this.id = id;
+    this.name = name;
+    this.price = price;
+    this.cost = cost;
+    this.supplier = supplier;
+  }
+
+  /**
+   * Constructor.
+   */
+  public Product() {
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public Product setId(Long id) {
+    this.id = id;
+    return this;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public Product setName(String name) {
+    this.name = name;
+    return this;
+  }
+
+  public Double getPrice() {
+    return price;
+  }
+
+  public Product setPrice(Double price) {
+    this.price = price;
+    return this;
+  }
+
+  public Double getCost() {
+    return cost;
+  }
+
+  public Product setCost(Double cost) {
+    this.cost = cost;
+    return this;
+  }
+
+  public String getSupplier() {
+    return supplier;
+  }
+
+  public Product setSupplier(String supplier) {
+    this.supplier = supplier;
+    return this;
+  }
+
+  @Override
+  public String toString() {
+    return "Product{"
+        + "id=" + id
+        + ", name='" + name + '\''
+        + ", price=" + price
+        + ", cost=" + cost
+        + ", supplier='" + supplier + '\''
+        + '}';
+  }
+}

data-transfer-object/src/main/java/com/iluwatar/datatransfer/product/ProductDto.java

@@ -0,0 +1,287 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.datatransfer.product;
+
+/**
+ * {@link ProductDto} is a data transfer object POJO.
+ * Instead of sending individual information to
+ * client We can send related information together in POJO.
+ *
+ * <p>Dto will not have any business logic in it.
+ */
+public enum ProductDto {
+  ;
+
+  /**
+   * This is Request class which consist of Create or any other request DTO's
+   * you might want to use in your API.
+   */
+  public enum Request {
+    ;
+
+    /**
+     * This is Create dto class for requesting create new product.
+     */
+    public static final class Create implements Name, Price, Cost, Supplier {
+      private String name;
+      private Double price;
+      private Double cost;
+      private String supplier;
+
+      @Override
+      public String getName() {
+        return name;
+      }
+
+      public Create setName(String name) {
+        this.name = name;
+        return this;
+      }
+
+      @Override
+      public Double getPrice() {
+        return price;
+      }
+
+      public Create setPrice(Double price) {
+        this.price = price;
+        return this;
+      }
+
+      @Override
+      public Double getCost() {
+        return cost;
+      }
+
+      public Create setCost(Double cost) {
+        this.cost = cost;
+        return this;
+      }
+
+      @Override
+      public String getSupplier() {
+        return supplier;
+      }
+
+      public Create setSupplier(String supplier) {
+        this.supplier = supplier;
+        return this;
+      }
+    }
+  }
+
+  /**
+   * This is Response class which consist of any response DTO's
+   * you might want to provide to your clients.
+   */
+  public enum Response {
+    ;
+
+    /**
+     * This is Public dto class for API response with the lowest data security.
+     */
+    public static final class Public implements Id, Name, Price {
+      private Long id;
+      private String name;
+      private Double price;
+
+      @Override
+      public Long getId() {
+        return id;
+      }
+
+      public Public setId(Long id) {
+        this.id = id;
+        return this;
+      }
+
+      @Override
+      public String getName() {
+        return name;
+      }
+
+      public Public setName(String name) {
+        this.name = name;
+        return this;
+      }
+
+      @Override
+      public Double getPrice() {
+        return price;
+      }
+
+      public Public setPrice(Double price) {
+        this.price = price;
+        return this;
+      }
+
+      @Override
+      public String toString() {
+        return "Public{"
+            + "id="
+            + id
+            + ", name='"
+            + name
+            + '\''
+            + ", price="
+            + price
+            + '}';
+      }
+    }
+
+    /**
+     * This is Private dto class for API response with the highest data security.
+     */
+    public static final class Private implements Id, Name, Price, Cost {
+      private Long id;
+      private String name;
+      private Double price;
+      private Double cost;
+
+      @Override
+      public Long getId() {
+        return id;
+      }
+
+      public Private setId(Long id) {
+        this.id = id;
+        return this;
+      }
+
+      @Override
+      public String getName() {
+        return name;
+      }
+
+      public Private setName(String name) {
+        this.name = name;
+        return this;
+      }
+
+      @Override
+      public Double getPrice() {
+        return price;
+      }
+
+      public Private setPrice(Double price) {
+        this.price = price;
+        return this;
+      }
+
+      @Override
+      public Double getCost() {
+        return cost;
+      }
+
+      public Private setCost(Double cost) {
+        this.cost = cost;
+        return this;
+      }
+
+      @Override
+      public String toString() {
+        return "Private{"
+            +
+            "id="
+            + id
+            +
+            ", name='"
+            + name
+            + '\''
+            +
+            ", price="
+            + price
+            +
+            ", cost="
+            + cost
+            +
+            '}';
+      }
+    }
+  }
+
+  /**
+   * Use this interface whenever you want to provide the product Id in your DTO.
+   */
+  private interface Id {
+    /**
+     * Unique identifier of the product.
+     *
+     * @return : id of the product.
+     */
+    Long getId();
+  }
+
+  /**
+   * Use this interface whenever you want to provide the product Name in your DTO.
+   */
+  private interface Name {
+    /**
+     * The name of the product.
+     *
+     * @return : name of the product.
+     */
+    String getName();
+  }
+
+  /**
+   * Use this interface whenever you want to provide the product Price in your DTO.
+   */
+  private interface Price {
+    /**
+     * The amount we sell a product for.
+     * <b>This data is not confidential</b>
+     *
+     * @return : price of the product.
+     */
+    Double getPrice();
+  }
+
+  /**
+   * Use this interface whenever you want to provide the product Cost in your DTO.
+   */
+  private interface Cost {
+    /**
+     * The amount that it costs us to purchase this product
+     * For the amount we sell a product for, see the {@link Price Price} parameter.
+     * <b>This data is confidential</b>
+     *
+     * @return : cost of the product.
+     */
+    Double getCost();
+  }
+
+  /**
+   * Use this interface whenever you want to provide the product Supplier in your DTO.
+   */
+  private interface Supplier {
+    /**
+     * The name of supplier of the product or its manufacturer.
+     * <b>This data is highly confidential</b>
+     *
+     * @return : supplier of the product.
+     */
+    String getSupplier();
+  }
+}

data-transfer-object/src/main/java/com/iluwatar/datatransfer/product/ProductResource.java

@@ -0,0 +1,94 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.datatransfer.product;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * The resource class which serves product information. This class act as server in the demo. Which
+ * has all product details.
+ */
+public class ProductResource {
+  private final List<Product> products;
+
+  /**
+   * Initialise resource with existing products.
+   *
+   * @param products initialize resource with existing products. Act as database.
+   */
+  public ProductResource(final List<Product> products) {
+    this.products = products;
+  }
+
+  /**
+   * Get all products.
+   *
+   * @return : all products in list but in the scheme of private dto.
+   */
+  public List<ProductDto.Response.Private> getAllProductsForAdmin() {
+    return products
+        .stream()
+        .map(p -> new ProductDto.Response.Private().setId(p.getId()).setName(p.getName())
+            .setCost(p.getCost())
+            .setPrice(p.getPrice()))
+        .collect(Collectors.toList());
+  }
+
+  /**
+   * Get all products.
+   *
+   * @return : all products in list but in the scheme of public dto.
+   */
+  public List<ProductDto.Response.Public> getAllProductsForCustomer() {
+    return products
+        .stream()
+        .map(p -> new ProductDto.Response.Public().setId(p.getId()).setName(p.getName())
+            .setPrice(p.getPrice()))
+        .collect(Collectors.toList());
+  }
+
+  /**
+   * Save new product.
+   *
+   * @param createProductDto save new product to list.
+   */
+  public void save(ProductDto.Request.Create createProductDto) {
+    products.add(new Product()
+        .setId((long) (products.size() + 1))
+        .setName(createProductDto.getName())
+        .setSupplier(createProductDto.getSupplier())
+        .setPrice(createProductDto.getPrice())
+        .setCost(createProductDto.getCost()));
+  }
+
+  /**
+   * List of all products in an entity representation.
+   *
+   * @return : all the products entity that stored in the products list
+   */
+  public List<Product> getProducts() {
+    return products;
+  }
+}

data-transfer-object/src/test/java/com/iluwatar/datatransfer/customer/CustomerResourceTest.java

@@ -21,13 +21,16 @@
  * THE SOFTWARE.
  */
 
-package com.iluwatar.datatransfer;
+package com.iluwatar.datatransfer.customer;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.ArrayList;
 import java.util.List;
+
+import com.iluwatar.datatransfer.customer.CustomerDto;
+import com.iluwatar.datatransfer.customer.CustomerResource;
 import org.junit.jupiter.api.Test;
 
 /**

decorator/README.md

@@ -10,30 +10,39 @@ tags:
 ---
 
 ## Also known as
+
 Wrapper
 
 ## Intent
-Attach additional responsibilities to an object dynamically.
-Decorators provide a flexible alternative to subclassing for extending
-functionality.
+
+Attach additional responsibilities to an object dynamically. Decorators provide a flexible 
+alternative to subclassing for extending functionality.
 
 ## Explanation
 
 Real world example
 
-> There is an angry troll living in the nearby hills. Usually it goes bare handed but sometimes it has a weapon. To arm the troll it's not necessary to create a new troll but to decorate it dynamically with a suitable weapon.
+> There is an angry troll living in the nearby hills. Usually it goes bare handed but sometimes it 
+> has a weapon. To arm the troll it's not necessary to create a new troll but to decorate it 
+> dynamically with a suitable weapon.
 
 In plain words
 
-> Decorator pattern lets you dynamically change the behavior of an object at run time by wrapping them in an object of a decorator class.
+> Decorator pattern lets you dynamically change the behavior of an object at run time by wrapping 
+> them in an object of a decorator class.
 
 Wikipedia says
 
-> In object-oriented programming, the decorator pattern is a design pattern that allows behavior to be added to an individual object, either statically or dynamically, without affecting the behavior of other objects from the same class. The decorator pattern is often useful for adhering to the Single Responsibility Principle, as it allows functionality to be divided between classes with unique areas of concern.
+> In object-oriented programming, the decorator pattern is a design pattern that allows behavior to 
+> be added to an individual object, either statically or dynamically, without affecting the behavior 
+> of other objects from the same class. The decorator pattern is often useful for adhering to the 
+> Single Responsibility Principle, as it allows functionality to be divided between classes with 
+> unique areas of concern.
 
 **Programmatic Example**
 
-Let's take the troll example. First of all we have a simple troll implementing the troll interface
+Let's take the troll example. First of all we have a `SimpleTroll` implementing the `Troll` 
+interface:
 
 ```java
 public interface Troll {
@@ -63,7 +72,7 @@ public class SimpleTroll implements Troll {
 }
 ```
 
-Next we want to add club for the troll. We can do it dynamically by using a decorator
+Next we want to add club for the troll. We can do it dynamically by using a decorator:
 
 ```java
 public class ClubbedTroll implements Troll {
@@ -94,7 +103,7 @@ public class ClubbedTroll implements Troll {
 }
 ```
 
-Here's the troll in action
+Here's the troll in action:
 
 ```java
 // simple troll
@@ -108,20 +117,36 @@ clubbedTroll.attack(); // The troll tries to grab you! The troll swings at you w
 clubbedTroll.fleeBattle(); // The troll shrieks in horror and runs away!
 ```
 
+Program output:
+
+```java
+The troll tries to grab you!
+The troll shrieks in horror and runs away!
+The troll tries to grab you! The troll swings at you with a club!
+The troll shrieks in horror and runs away!
+```
+
 ## Class diagram
+
 ![alt text](./etc/decorator.urm.png "Decorator pattern class diagram")
 
 ## Applicability
-Use Decorator
 
-* To add responsibilities to individual objects dynamically and transparently, that is, without affecting other objects
-* For responsibilities that can be withdrawn
-* When extension by subclassing is impractical. Sometimes a large number of independent extensions are possible and would produce an explosion of subclasses to support every combination. Or a class definition may be hidden or otherwise unavailable for subclassing
+Decorator is used to:
+
+* Add responsibilities to individual objects dynamically and transparently, that is, without 
+affecting other objects.
+* For responsibilities that can be withdrawn.
+* When extension by subclassing is impractical. Sometimes a large number of independent extensions 
+are possible and would produce an explosion of subclasses to support every combination. Or a class 
+definition may be hidden or otherwise unavailable for subclassing.
 
 ## Tutorial
+
 * [Decorator Pattern Tutorial](https://www.journaldev.com/1540/decorator-design-pattern-in-java-example)
 
 ## Real world examples
+
  * [java.io.InputStream](http://docs.oracle.com/javase/8/docs/api/java/io/InputStream.html), [java.io.OutputStream](http://docs.oracle.com/javase/8/docs/api/java/io/OutputStream.html),
  [java.io.Reader](http://docs.oracle.com/javase/8/docs/api/java/io/Reader.html) and [java.io.Writer](http://docs.oracle.com/javase/8/docs/api/java/io/Writer.html)
  * [java.util.Collections#synchronizedXXX()](http://docs.oracle.com/javase/8/docs/api/java/util/Collections.html#synchronizedCollection-java.util.Collection-)

decorator/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>decorator</artifactId>
   <dependencies>

delegation/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
 

dependency-injection/README.md

@@ -9,15 +9,19 @@ tags:
 ---
 
 ## Intent
-Dependency Injection is a software design pattern in which one or more dependencies (or services) are injected, or 
-passed by reference, into a dependent object (or client) and are made part of the client's state. The pattern separates 
-the creation of a client's dependencies from its own behavior, which allows program designs to be loosely coupled and 
-to follow the inversion of control and single responsibility principles.
+
+Dependency Injection is a software design pattern in which one or more dependencies (or services) 
+are injected, or passed by reference, into a dependent object (or client) and are made part of the 
+client's state. The pattern separates the creation of a client's dependencies from its own behavior, 
+which allows program designs to be loosely coupled and to follow the inversion of control and single 
+responsibility principles.
 
 ## Explanation
+
 Real world example
 
-> The old wizard likes to fill his pipe and smoke tobacco once in a while. However, he doesn't want to depend on a single tobacco brand only but likes to be able to enjoy them all interchangeably.    
+> The old wizard likes to fill his pipe and smoke tobacco once in a while. However, he doesn't want 
+> to depend on a single tobacco brand only but likes to be able to enjoy them all interchangeably.    
 
 In plain words
 
@@ -25,11 +29,12 @@ In plain words
 
 Wikipedia says
 
-> In software engineering, dependency injection is a technique in which an object receives other objects that it depends on. These other objects are called dependencies.
+> In software engineering, dependency injection is a technique in which an object receives other 
+> objects that it depends on. These other objects are called dependencies.
 
 **Programmatic Example**
 
-Let's first introduce the tobacco brands.
+Let's first introduce the `Tobacco` interface and the concrete brands.
 
 ```java
 public abstract class Tobacco {
@@ -52,7 +57,7 @@ public class OldTobyTobacco extends Tobacco {
 }
 ```
 
-Next here's the wizard class hierarchy.
+Next here's the `Wizard` class hierarchy.
 
 ```java
 public interface Wizard {
@@ -83,13 +88,15 @@ And lastly we can show how easy it is to give the old wizard any brand of tobacc
 ```
 
 ## Class diagram
+
 ![alt text](./etc/dependency-injection.png "Dependency Injection")
 
 ## Applicability
-Use the Dependency Injection pattern when
 
-* When you need to remove knowledge of concrete implementation from object
-* To enable unit testing of classes in isolation using mock objects or stubs
+Use the Dependency Injection pattern when:
+
+* When you need to remove knowledge of concrete implementation from object.
+* To enable unit testing of classes in isolation using mock objects or stubs.
 
 ## Credits
 

dependency-injection/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>dependency-injection</artifactId>
   <dependencies>

dirty-flag/pom.xml

@@ -29,10 +29,10 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>dirty-flag</artifactId>
-  <version>1.23.0-SNAPSHOT</version>
+  <version>1.24.0-SNAPSHOT</version>
   <name>dirty-flag</name>
   <url>http://maven.apache.org</url>
   <properties>

double-buffer/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.23.0-SNAPSHOT</version>
+        <version>1.24.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

double-checked-locking/pom.xml

@@ -27,7 +27,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>double-checked-locking</artifactId>
   <dependencies>

double-dispatch/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.23.0-SNAPSHOT</version>
+    <version>1.24.0-SNAPSHOT</version>
   </parent>
   <artifactId>double-dispatch</artifactId>
   <dependencies>

double-dispatch/src/main/java/com/iluwatar/doubledispatch/SpaceStationMir.java

@@ -45,7 +45,7 @@ public class SpaceStationMir extends GameObject {
 
   @Override
   public void collisionResolve(FlamingAsteroid asteroid) {
-    LOGGER.info(AppConstants.HITS, " {} is damaged! {} is set on fire!", asteroid.getClass()
+    LOGGER.info(AppConstants.HITS + " {} is damaged! {} is set on fire!", asteroid.getClass()
             .getSimpleName(),
         this.getClass().getSimpleName(), this.getClass().getSimpleName(), this.getClass()
             .getSimpleName());
@@ -55,14 +55,14 @@ public class SpaceStationMir extends GameObject {
 
   @Override
   public void collisionResolve(Meteoroid meteoroid) {
-    LOGGER.info(AppConstants.HITS, " {} is damaged!", meteoroid.getClass().getSimpleName(),
+    LOGGER.info(AppConstants.HITS + " {} is damaged!", meteoroid.getClass().getSimpleName(),
         this.getClass().getSimpleName(), this.getClass().getSimpleName());
     setDamaged(true);
   }
 
   @Override
   public void collisionResolve(SpaceStationMir mir) {
-    LOGGER.info(AppConstants.HITS, " {} is damaged!", mir.getClass().getSimpleName(),
+    LOGGER.info(AppConstants.HITS + " {} is damaged!", mir.getClass().getSimpleName(),
         this.getClass().getSimpleName(), this.getClass().getSimpleName());
     setDamaged(true);
   }