docs: update .all-contributorsrc [skip ci]

* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>

.all-contributorsrc

@@ -0,0 +1,184 @@
+{
+  "files": [
+    "README.md"
+  ],
+  "imageSize": 100,
+  "commit": false,
+  "contributors": [
+    {
+      "login": "iluwatar",
+      "name": "Ilkka Seppälä",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/582346?v=4",
+      "profile": "https://github.com/iluwatar",
+      "contributions": [
+        "projectManagement",
+        "maintenance",
+        "content"
+      ]
+    },
+    {
+      "login": "amit1307",
+      "name": "amit1307",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/23420222?v=4",
+      "profile": "https://github.com/amit1307",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "npathai",
+      "name": "Narendra Pathai",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/1792515?v=4",
+      "profile": "https://github.com/npathai",
+      "contributions": [
+        "code",
+        "ideas",
+        "review"
+      ]
+    },
+    {
+      "login": "fluxw42",
+      "name": "Jeroen Meulemeester",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/1545460?v=4",
+      "profile": "https://github.com/fluxw42",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "mikulucky",
+      "name": "Joseph McCarthy",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/4526195?v=4",
+      "profile": "http://www.joemccarthy.co.uk",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "thomasoss",
+      "name": "Thomas",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/22516154?v=4",
+      "profile": "https://github.com/thomasoss",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "anuragagarwal561994",
+      "name": "Anurag Agarwal",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/6075379?v=4",
+      "profile": "https://github.com/anuragagarwal561994",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "markusmo3",
+      "name": "Markus Moser",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/3317416?v=4",
+      "profile": "https://markusmo3.github.io",
+      "contributions": [
+        "design",
+        "code",
+        "ideas"
+      ]
+    },
+    {
+      "login": "isabiq",
+      "name": "Sabiq Ihab",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/19510920?v=4",
+      "profile": "https://twitter.com/i_sabiq",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "inbravo",
+      "name": "Amit Dixit",
+      "avatar_url": "https://avatars3.githubusercontent.com/u/5253764?v=4",
+      "profile": "http://inbravo.github.io",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "piyushchaudhari04",
+      "name": "Piyush Kailash Chaudhari",
+      "avatar_url": "https://avatars3.githubusercontent.com/u/10268029?v=4",
+      "profile": "https://github.com/piyushchaudhari04",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "joshzambales",
+      "name": "joshzambales",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/8704552?v=4",
+      "profile": "https://github.com/joshzambales",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "Crossy147",
+      "name": "Kamil Pietruszka",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/7272996?v=4",
+      "profile": "https://github.com/Crossy147",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "zafarella",
+      "name": "Zafar Khaydarov",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/660742?v=4",
+      "profile": "http://cs.joensuu.fi/~zkhayda",
+      "contributions": [
+        "code",
+        "doc"
+      ]
+    },
+    {
+      "login": "kemitix",
+      "name": "Paul Campbell",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/1147749?v=4",
+      "profile": "https://kemitix.github.io/",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "Argyro-Sioziou",
+      "name": "Argyro Sioziou",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/22822639?v=4",
+      "profile": "https://github.com/Argyro-Sioziou",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "TylerMcConville",
+      "name": "TylerMcConville",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/4946449?v=4",
+      "profile": "https://github.com/TylerMcConville",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "saksham93",
+      "name": "saksham93",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/37399540?v=4",
+      "profile": "https://github.com/saksham93",
+      "contributions": [
+        "code"
+      ]
+    }
+  ],
+  "contributorsPerLine": 7,
+  "projectName": "java-design-patterns",
+  "projectOwner": "iluwatar",
+  "repoType": "github",
+  "repoHost": "https://github.com",
+  "skipCi": true
+}

.github/workflows/maven.yml

@@ -0,0 +1,60 @@
+#
+# 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.
+#
+
+# This workflow will build a Java project with Maven
+# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven
+
+name: Java CI with Maven
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-18.04
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK 11
+      uses: actions/setup-java@v1
+      with:
+        java-version: 11
+    # Some tests need screen access
+    - name: Install xvfb
+      run: sudo apt-get install xvfb
+    # 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
+    - 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 }}
+        SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

.travis.yml

@@ -1,36 +0,0 @@
-language: java
-dist: bionic
-jdk:
-- openjdk11
-sudo: required
-
-env:
-  global:
-  - secure: "DCpazS3nkLnter3sguXEAS2fC/1ZWNfM+XLyif9MfNFxlZdpni2vCD/jA0Rdpga8puQWHNVLyAec+RPFH/2qSmJ1c1UTV5MaLv8tPqwUX0VFA+1I6XoSv6oX4ldHTBWHEWqQHkRFOLoil0h0edc0tTOWQwXF8U+DLAB+HkRb4gw="
-
-services:
-- xvfb
-
-addons:
-  sonarcloud:
-    organization: "iluwatar"
-    token:
-      secure: "FpHwMYPMkdWU6CeIB7+O3qIeIM4vJMp47UjkKK53f0w0s6tPZofZZkab+gcL2TqKSil7sFVB/AQXU1cUubflRszwcLbNsc8H2yFehD79o0o0Mqd1Dd5ip/q0KQbHkkln+InFlVLfvrLB4Xd4mlQVxbGhqpULBhXjKzFzQlRFcuU="
-script:
-  # Because of Travis security restrictions, SonarCloud analysis cannot be run on pull requests originated from forks
-  # See https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions
-  - 'if [ "$TRAVIS_PULL_REQUEST" != "false" ]; then mvn clean verify; fi'
-  - 'if [ "$TRAVIS_PULL_REQUEST" = "false" ]; then mvn clean verify sonar:sonar -Dsonar.projectKey=iluwatar_java-design-patterns -Dsonar.host.url=https://sonarcloud.io; fi'
-
-after_success:
-- bash update-website.sh
-
-notifications:
-  email:
-    - iluwatar@gmail.com
-  webhooks:
-    urls:
-      - https://webhooks.gitter.im/e/3319623945358a093a6f
-    on_success: change  # options: [always|never|change] default: always
-    on_failure: always  # options: [always|never|change] default: always
-    on_start: never     # options: [always|never|change] default: always

LICENSE.md

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2014-2016 Ilkka Seppälä
+Copyright (c) 2014-2020 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

README.md

@@ -4,10 +4,13 @@
 
 # Design patterns implemented in Java
 
-[![Build status](https://travis-ci.org/iluwatar/java-design-patterns.svg?branch=master)](https://travis-ci.org/iluwatar/java-design-patterns)
+![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)
 [![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-18-orange.svg?style=flat-square)](#contributors-)
+<!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 # Introduction
 
@@ -31,19 +34,20 @@ programming tutorials 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
-software design principles.
+[Software Design Principles](https://java-design-patterns.com/principles/).
 
 All designs should be as simple as possible. You should start with KISS, YAGNI,
 and Do The Simplest Thing That Could Possibly Work principles. Complexity and
 patterns should only be introduced when they are needed for practical
 extensibility.
 
-Once you are familiar with these concepts you can start drilling down into
+Once you are familiar with these concepts you can start drilling down into the
-patterns by any of the following approaches
+[available design patterns](https://java-design-patterns.com/patterns/) by any 
+of the following approaches
 
- - Using difficulty tags, `Difficulty-Beginner`, `Difficulty-Intermediate` & `Difficulty-Expert`.
+ - Search for a specific pattern by name. Can't find one? Please report a new pattern [here](https://github.com/iluwatar/java-design-patterns/issues).
+ - Using tags such as `Performance`, `Gang of Four` or `Data access`.
  - Using pattern categories, `Creational`, `Behavioral`, and others.
- - Search for a specific pattern. Can't find one? Please report a new pattern [here](https://github.com/iluwatar/java-design-patterns/issues).
 
 Hopefully you find the object oriented solutions presented on this site useful
 in your architectures and have as much fun learning them as we had developing them.
@@ -57,3 +61,41 @@ you and answer your questions in the [Gitter chatroom](https://gitter.im/iluwata
 # License
 
 This project is licensed under the terms of the MIT license.
+
+# Contributors
+
+<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
+<!-- prettier-ignore-start -->
+<!-- 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="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>
+  </tr>
+  <tr>
+    <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="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://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>
+  </tr>
+  <tr>
+    <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/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>
+  </tr>
+</table>
+
+<!-- markdownlint-enable -->
+<!-- prettier-ignore-end -->
+<!-- ALL-CONTRIBUTORS-LIST:END -->
+
+This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!

abstract-document/README.md

@@ -5,13 +5,13 @@ folder: abstract-document
 permalink: /patterns/abstract-document/
 categories: Structural
 tags: 
- - Java
+ - Extensibility
- - Difficulty-Intermediate
 ---
 
 ## Intent
 Achieve flexibility of untyped languages and keep the type-safety 
 
+## Class diagram
 ![alt text](./etc/abstract-document.png "Abstract Document Traits and Domain")
 
 
@@ -26,4 +26,4 @@ Use the Abstract Document Pattern when
 ## Credits
 
 * [Wikipedia: Abstract Document Pattern](https://en.wikipedia.org/wiki/Abstract_Document_Pattern)
-* [Martin Fowler: Dealing with properties](http://martinfowler.com/apsupp/properties.pdf)
+* [Martin Fowler: Dealing with properties](http://martinfowler.com/apsupp/properties.pdf)

abstract-document/etc/abstract-document.urm.puml

@@ -0,0 +1,65 @@
+@startuml
+package com.iluwatar.abstractdocument.domain.enums {
+  enum Property {
+    + MODEL {static}
+    + PARTS {static}
+    + PRICE {static}
+    + TYPE {static}
+    + valueOf(name : String) : Property {static}
+    + values() : Property[] {static}
+  }
+}
+package com.iluwatar.abstractdocument.domain {
+  class Car {
+    + Car(properties : Map<String, Object>)
+  }
+  interface HasModel {
+    + getModel() : Optional<String>
+  }
+  interface HasParts {
+    + getParts() : Stream<Part>
+  }
+  interface HasPrice {
+    + getPrice() : Optional<Number>
+  }
+  interface HasType {
+    + getType() : Optional<String>
+  }
+  class Part {
+    + Part(properties : Map<String, Object>)
+  }
+}
+package com.iluwatar.abstractdocument {
+  abstract class AbstractDocument {
+    - properties : Map<String, Object>
+    # AbstractDocument(properties : Map<String, Object>)
+    + children(key : String, constructor : Function<Map<String, Object>, T>) : Stream<T>
+    + get(key : String) : Object
+    + put(key : String, value : Object)
+    + toString() : String
+  }
+  class App {
+    - LOGGER : Logger {static}
+    + App()
+    + main(args : String[]) {static}
+  }
+  interface Document {
+    + children(String, Function<Map<String, Object>, T>) : Stream<T> {abstract}
+    + get(String) : Object {abstract}
+    + put(String, Object) {abstract}
+  }
+}
+AbstractDocument ..|> Document 
+Car ..|> HasModel 
+Car ..|> HasPrice 
+Car ..|> HasParts 
+Car --|> AbstractDocument 
+HasModel --|> Document 
+HasParts --|> Document 
+HasPrice --|> Document 
+HasType --|> Document 
+Part ..|> HasType 
+Part ..|> HasModel 
+Part ..|> HasPrice 
+Part --|> AbstractDocument 
+@enduml

abstract-document/pom.xml

@@ -1,42 +1,55 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN THE SOFTWARE. -->
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+<project xmlns="http://maven.apache.org/POM/4.0.0"
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	<modelVersion>4.0.0</modelVersion>
-    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	<parent>
-    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+		<artifactId>java-design-patterns</artifactId>
-    THE SOFTWARE.
+		<groupId>com.iluwatar</groupId>
-
+		<version>1.23.0-SNAPSHOT</version>
--->
+	</parent>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	<artifactId>abstract-document</artifactId>
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<dependencies>
-    <modelVersion>4.0.0</modelVersion>
+		<dependency>
-    <parent>
+			<groupId>org.junit.jupiter</groupId>
-        <artifactId>java-design-patterns</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-        <groupId>com.iluwatar</groupId>
+			<scope>test</scope>
-        <version>1.22.0-SNAPSHOT</version>
+		</dependency>
-    </parent>
+	</dependencies>
-    <artifactId>abstract-document</artifactId>
+	<build>
-    <dependencies>
+		<plugins>
-        <dependency>
+			<!-- Maven assembly plugin is invoked with default setting which we have 
-            <groupId>org.junit.jupiter</groupId>
+				in parent pom and specifying the class having main method -->
-            <artifactId>junit-jupiter-engine</artifactId>
+			<plugin>
-            <scope>test</scope>
+				<groupId>org.apache.maven.plugins</groupId>
-        </dependency>
+				<artifactId>maven-assembly-plugin</artifactId>
-    </dependencies>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.abstractdocument.App</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

abstract-document/src/main/java/com/iluwatar/abstractdocument/module-info.java

@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */
+
+module com.iluwatar.abstractdocument {
+	requires org.slf4j;
+}

abstract-factory/README.md

@@ -5,9 +5,7 @@ folder: abstract-factory
 permalink: /patterns/abstract-factory/
 categories: Creational
 tags:
- - Java
+ - Gang of Four
- - Gang Of Four
- - Difficulty-Intermediate
 ---
 
 ## Also known as
@@ -157,6 +155,9 @@ public static void main(String[] args) {
 }
 ```
 
+## Class diagram
+![alt text](./etc/abstract-factory.urm.png "Abstract Factory class diagram")
+
 
 ## Applicability
 Use the Abstract Factory pattern when
@@ -197,4 +198,5 @@ Use the Abstract Factory pattern when
 
 ## Credits
 
-* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://www.amazon.com/gp/product/0201633612/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0201633612&linkCode=as2&tag=javadesignpat-20&linkId=675d49790ce11db99d90bde47f1aeb59)
+* [Head First Design Patterns: A Brain-Friendly Guide](https://www.amazon.com/gp/product/0596007124/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596007124&linkCode=as2&tag=javadesignpat-20&linkId=6b8b6eea86021af6c8e3cd3fc382cb5b)

abstract-factory/etc/abstract-factory.urm.puml

@@ -0,0 +1,101 @@
+@startuml
+package com.iluwatar.abstractfactory {
+  class App {
+    - LOGGER : Logger {static}
+    - army : Army
+    - castle : Castle
+    - king : King
+    + App()
+    + createKingdom(factory : KingdomFactory)
+    + getArmy() : Army
+    ~ getArmy(factory : KingdomFactory) : Army
+    + getCastle() : Castle
+    ~ getCastle(factory : KingdomFactory) : Castle
+    + getKing() : King
+    ~ getKing(factory : KingdomFactory) : King
+    + main(args : String[]) {static}
+    - setArmy(army : Army)
+    - setCastle(castle : Castle)
+    - setKing(king : King)
+  }
+  class FactoryMaker {
+    + FactoryMaker()
+    + makeFactory(type : KingdomType) : KingdomFactory {static}
+  }
+  enum KingdomType {
+    + ELF {static}
+    + ORC {static}
+    + valueOf(name : String) : KingdomType {static}
+    + values() : KingdomType[] {static}
+  }
+  interface Army {
+    + getDescription() : String {abstract}
+  }
+  interface Castle {
+    + getDescription() : String {abstract}
+  }
+  class ElfArmy {
+    ~ DESCRIPTION : String {static}
+    + ElfArmy()
+    + getDescription() : String
+  }
+  class ElfCastle {
+    ~ DESCRIPTION : String {static}
+    + ElfCastle()
+    + getDescription() : String
+  }
+  class ElfKing {
+    ~ DESCRIPTION : String {static}
+    + ElfKing()
+    + getDescription() : String
+  }
+  class ElfKingdomFactory {
+    + ElfKingdomFactory()
+    + createArmy() : Army
+    + createCastle() : Castle
+    + createKing() : King
+  }
+  interface King {
+    + getDescription() : String {abstract}
+  }
+  interface KingdomFactory {
+    + createArmy() : Army {abstract}
+    + createCastle() : Castle {abstract}
+    + createKing() : King {abstract}
+  }
+  class OrcArmy {
+    ~ DESCRIPTION : String {static}
+    + OrcArmy()
+    + getDescription() : String
+  }
+  class OrcCastle {
+    ~ DESCRIPTION : String {static}
+    + OrcCastle()
+    + getDescription() : String
+  }
+  class OrcKing {
+    ~ DESCRIPTION : String {static}
+    + OrcKing()
+    + getDescription() : String
+  }
+  class OrcKingdomFactory {
+    + OrcKingdomFactory()
+    + createArmy() : Army
+    + createCastle() : Castle
+    + createKing() : King
+  }
+}
+KingdomType ..+ FactoryMaker
+App -->  "-castle" Castle
+FactoryMaker ..+ App
+App -->  "-king" King
+App -->  "-army" Army
+ElfArmy ..|> Army 
+ElfCastle ..|> Castle 
+ElfKing ..|> King 
+ElfKingdomFactory ..|> KingdomFactory 
+OrcArmy ..|> Army 
+OrcCastle ..|> Castle 
+OrcKing ..|> King 
+OrcKingdomFactory ..|> KingdomFactory 
+@enduml

abstract-factory/pom.xml

@@ -1,42 +1,56 @@
 <?xml version="1.0"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN THE SOFTWARE. -->
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+<project
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	xmlns="http://maven.apache.org/POM/4.0.0"
-    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	<modelVersion>4.0.0</modelVersion>
-    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+	<parent>
-    THE SOFTWARE.
+		<groupId>com.iluwatar</groupId>
-
+		<artifactId>java-design-patterns</artifactId>
--->
+		<version>1.23.0-SNAPSHOT</version>
-<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+	</parent>
-    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+	<artifactId>abstract-factory</artifactId>
-  <modelVersion>4.0.0</modelVersion>
+	<dependencies>
-  <parent>
+		<dependency>
-    <groupId>com.iluwatar</groupId>
+			<groupId>org.junit.jupiter</groupId>
-    <artifactId>java-design-patterns</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-    <version>1.22.0-SNAPSHOT</version>
+			<scope>test</scope>
-  </parent>
+		</dependency>
-  <artifactId>abstract-factory</artifactId>
+	</dependencies>
-  <dependencies>
+	<build>
-    <dependency>
+		<plugins>
-      <groupId>org.junit.jupiter</groupId>
+			<!-- Maven assembly plugin is invoked with default setting which we have 
-      <artifactId>junit-jupiter-engine</artifactId>
+				in parent pom and specifying the class having main method -->
-      <scope>test</scope>
+			<plugin>
-    </dependency>
+				<groupId>org.apache.maven.plugins</groupId>
-  </dependencies>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.abstractfactory.App</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

abstract-factory/src/main/java/com/iluwatar/abstractfactory/module-info.java

@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */
+
+module com.iluwatar.abstractfactory {
+	requires org.slf4j;
+}

acyclic-visitor/README.md

@@ -5,17 +5,18 @@ folder: acyclic-visitor
 permalink: /patterns/acyclic-visitor/
 categories: Behavioral
 tags:
- - Java
+ - Extensibility
- - Difficulty-Intermediate
 ---
 
-![alt text](./etc/acyclic-visitor.png "Acyclic Visitor")
-
 ## Intent
 Allow new functions to be added to existing class hierarchies without affecting those hierarchies, and without creating the troublesome dependency cycles that are inherent to the GOF VISITOR Pattern.
 
+## Class diagram
+![alt text](./etc/acyclic-visitor.png "Acyclic Visitor")
+
 ## Applicability
 This pattern can be used:
+
 * When you need to add a new function to an existing hierarchy without the need to alter or affect that hierarchy.
 * When there are functions that operate upon a hierarchy, but which do not belong in the hierarchy itself. e.g. the ConfigureForDOS / ConfigureForUnix / ConfigureForX issue.
 * When you need to perform very different operations on an object depending upon its type.
@@ -24,11 +25,13 @@ This pattern can be used:
 
 ## Consequences
 The good:
+
 * No dependency cycles between class hierarchies.
 * No need to recompile all the visitors if a new one is added.
 * Does not cause compilation failure in existing visitors if class hierarchy has a new member.
 
 The bad:
+
 * Violates the principle of least surprise or Liskov's Substitution principle by showing that it can accept all visitors but actually only being interested in particular visitors.
 * Parallel hierarchy of visitors has to be created for all members in visitable class hierarchy.
 

acyclic-visitor/etc/acyclic-visitor.urm.puml

@@ -0,0 +1,53 @@
+@startuml
+package com.iluwatar.acyclicvisitor {
+  interface AllModemVisitor {
+  }
+  class App {
+    + App()
+    + main(args : String[]) {static}
+  }
+  class ConfigureForDosVisitor {
+    - LOGGER : Logger {static}
+    + ConfigureForDosVisitor()
+    + visit(hayes : Hayes)
+    + visit(zoom : Zoom)
+  }
+  class ConfigureForUnixVisitor {
+    - LOGGER : Logger {static}
+    + ConfigureForUnixVisitor()
+    + visit(zoom : Zoom)
+  }
+  class Hayes {
+    - LOGGER : Logger {static}
+    + Hayes()
+    + accept(modemVisitor : ModemVisitor)
+    + toString() : String
+  }
+  interface HayesVisitor {
+    + visit(Hayes) {abstract}
+  }
+  abstract class Modem {
+    + Modem()
+    + accept(ModemVisitor) {abstract}
+  }
+  interface ModemVisitor {
+  }
+  class Zoom {
+    - LOGGER : Logger {static}
+    + Zoom()
+    + accept(modemVisitor : ModemVisitor)
+    + toString() : String
+  }
+  interface ZoomVisitor {
+    + visit(Zoom) {abstract}
+  }
+}
+AllModemVisitor --|> ZoomVisitor 
+AllModemVisitor --|> HayesVisitor 
+ConfigureForDosVisitor ..|> AllModemVisitor 
+ConfigureForUnixVisitor ..|> ZoomVisitor 
+Hayes --|> Modem 
+HayesVisitor --|> ModemVisitor 
+Zoom --|> Modem 
+ZoomVisitor --|> ModemVisitor 
+@enduml

acyclic-visitor/pom.xml

@@ -1,38 +1,29 @@
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN 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.
-
--->
 <project xmlns="http://maven.apache.org/POM/4.0.0"
 	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 	<modelVersion>4.0.0</modelVersion>
-	
+
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.22.0-SNAPSHOT</version>
+		<version>1.23.0-SNAPSHOT</version>
 	</parent>
-	
+
 	<artifactId>acyclic-visitor</artifactId>
 
 	<properties>
@@ -53,19 +44,40 @@
 		<dependency>
 			<groupId>uk.org.lidalia</groupId>
 			<artifactId>slf4j-test</artifactId>
-			<version>1.0.0</version>
+			<version>1.2.0</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.junit.jupiter</groupId>
+			<artifactId>junit-jupiter-engine</artifactId>
 			<scope>test</scope>
 		</dependency>
-    	<dependency>
-      		<groupId>org.junit.jupiter</groupId>
-      		<artifactId>junit-jupiter-engine</artifactId>
-      		<scope>test</scope>
-    	</dependency>
 		<dependency>
 			<groupId>org.mockito</groupId>
 			<artifactId>mockito-all</artifactId>
-			<version>1.9.5</version>
+			<version>1.10.19</version>
 			<scope>test</scope>
 		</dependency>
 	</dependencies>
+	<build>
+    <plugins>
+      <!-- Maven assembly plugin is invoked with default setting which we have 
+        in parent pom and specifying the class having main method -->
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.acyclicvisitor.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
 </project>

acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/module-info.java

@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */
+
+module com.iluwatar.acyclicvisitor {
+	requires org.slf4j;
+}

adapter/README.md

@@ -5,9 +5,7 @@ folder: adapter
 permalink: /patterns/adapter/
 categories: Structural
 tags:
- - Java
+ - Gang of Four
- - Gang Of Four
- - Difficulty-Beginner
 ---
 
 ## Also known as
@@ -97,6 +95,9 @@ var captain = new Captain(new FishingBoatAdapter());
 captain.row();
 ```
 
+## Class diagram
+![alt text](./etc/adapter.urm.png "Adapter class diagram")
+
 ## Applicability
 Use the Adapter pattern when
 
@@ -128,5 +129,7 @@ An object adapter
 
 ## Credits
 
-* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://www.amazon.com/gp/product/0201633612/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0201633612&linkCode=as2&tag=javadesignpat-20&linkId=675d49790ce11db99d90bde47f1aeb59)
-* [J2EE Design Patterns](http://www.amazon.com/J2EE-Design-Patterns-William-Crawford/dp/0596004273/ref=sr_1_2)
+* [J2EE Design Patterns](https://www.amazon.com/gp/product/0596004273/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596004273&linkCode=as2&tag=javadesignpat-20&linkId=48d37c67fb3d845b802fa9b619ad8f31)
+* [Head First Design Patterns: A Brain-Friendly Guide](https://www.amazon.com/gp/product/0596007124/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596007124&linkCode=as2&tag=javadesignpat-20&linkId=6b8b6eea86021af6c8e3cd3fc382cb5b)
+* [Refactoring to Patterns](https://www.amazon.com/gp/product/0321213351/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0321213351&linkCode=as2&tag=javadesignpat-20&linkId=2a76fcb387234bc71b1c61150b3cc3a7)

adapter/etc/adapter.urm.puml

@@ -0,0 +1,31 @@
+@startuml
+package com.iluwatar.adapter {
+  class App {
+    - App()
+    + main(args : String[]) {static}
+  }
+  class Captain {
+    - rowingBoat : RowingBoat
+    + Captain()
+    + Captain(boat : RowingBoat)
+    ~ row()
+    ~ setRowingBoat(boat : RowingBoat)
+  }
+  ~class FishingBoat {
+    - LOGGER : Logger {static}
+    ~ FishingBoat()
+    ~ sail()
+  }
+  class FishingBoatAdapter {
+    - boat : FishingBoat
+    + FishingBoatAdapter()
+    + row()
+  }
+  interface RowingBoat {
+    + row() {abstract}
+  }
+}
+FishingBoatAdapter -->  "-boat" FishingBoat
+Captain -->  "-rowingBoat" RowingBoat
+FishingBoatAdapter ..|> RowingBoat 
+@enduml

adapter/pom.xml

@@ -1,47 +1,61 @@
 <?xml version="1.0"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN THE SOFTWARE. -->
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+<project
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	xmlns="http://maven.apache.org/POM/4.0.0"
-    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	<modelVersion>4.0.0</modelVersion>
-    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+	<parent>
-    THE SOFTWARE.
+		<groupId>com.iluwatar</groupId>
-
+		<artifactId>java-design-patterns</artifactId>
--->
+		<version>1.23.0-SNAPSHOT</version>
-<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+	</parent>
-    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+	<artifactId>adapter</artifactId>
-  <modelVersion>4.0.0</modelVersion>
+	<dependencies>
-  <parent>
+		<dependency>
-    <groupId>com.iluwatar</groupId>
+			<groupId>org.junit.jupiter</groupId>
-    <artifactId>java-design-patterns</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-    <version>1.22.0-SNAPSHOT</version>
+			<scope>test</scope>
-  </parent>
+		</dependency>
-  <artifactId>adapter</artifactId>
+		<dependency>
-  <dependencies>
+			<groupId>org.mockito</groupId>
-    <dependency>
+			<artifactId>mockito-core</artifactId>
-      <groupId>org.junit.jupiter</groupId>
+			<scope>test</scope>
-      <artifactId>junit-jupiter-engine</artifactId>
+		</dependency>
-      <scope>test</scope>
+	</dependencies>
-    </dependency>
+	<build>
-    <dependency>
+		<plugins>
-      <groupId>org.mockito</groupId>
+			<!-- Maven assembly plugin is invoked with default setting which we have 
-      <artifactId>mockito-core</artifactId>
+				in parent pom and specifying the class having main method -->
-      <scope>test</scope>
+			<plugin>
-    </dependency>
+				<groupId>org.apache.maven.plugins</groupId>
-  </dependencies>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.adapter.App</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

aggregator-microservices/README.md

@@ -5,8 +5,7 @@ folder: aggregator-microservices
 permalink: /patterns/aggregator-microservices/
 categories: Architectural
 tags:
-- Java
+- Cloud distributed
-- Spring
 ---
 
 ## Intent
@@ -18,6 +17,8 @@ More variations of the aggregator are:
 - Chained Microservice Design Pattern: In this case each microservice is dependent/ chained to a series 
 of other microservices.
 
+## Class diagram
+
 ![alt text](./etc/aggregator-microservice.png "Aggregator Microservice")
 
 ## Applicability
@@ -26,4 +27,4 @@ Use the Aggregator Microservices pattern when you need a unified API for various
 
 ## Credits
 
-* [Microservice Design Patterns](http://blog.arungupta.me/microservice-design-patterns/)
+* [Microservice Design Patterns](http://web.archive.org/web/20190705163602/http://blog.arungupta.me/microservice-design-patterns/)

aggregator-microservices/aggregator-service/etc/aggregator-service.urm.puml

@@ -0,0 +1,43 @@
+@startuml
+package com.iluwatar.aggregator.microservices {
+  class Aggregator {
+    - informationClient : ProductInformationClient
+    - inventoryClient : ProductInventoryClient
+    + Aggregator()
+    + getProduct() : Product
+  }
+  class App {
+    + App()
+    + main(args : String[]) {static}
+  }
+  class Product {
+    - productInventories : int
+    - title : String
+    + Product()
+    + getProductInventories() : int
+    + getTitle() : String
+    + setProductInventories(productInventories : int)
+    + setTitle(title : String)
+  }
+  interface ProductInformationClient {
+    + getProductTitle() : String {abstract}
+  }
+  class ProductInformationClientImpl {
+    - LOGGER : Logger {static}
+    + ProductInformationClientImpl()
+    + getProductTitle() : String
+  }
+  interface ProductInventoryClient {
+    + getProductInventories() : Integer {abstract}
+  }
+  class ProductInventoryClientImpl {
+    - LOGGER : Logger {static}
+    + ProductInventoryClientImpl()
+    + getProductInventories() : Integer
+  }
+}
+Aggregator -->  "-informationClient" ProductInformationClient
+Aggregator -->  "-inventoryClient" ProductInventoryClient
+ProductInformationClientImpl ..|> ProductInformationClient 
+ProductInventoryClientImpl ..|> ProductInventoryClient 
+@enduml

aggregator-microservices/aggregator-service/pom.xml

@@ -1,73 +1,81 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN 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.
-
--->
 <project xmlns="http://maven.apache.org/POM/4.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <parent>
+	<parent>
-        <artifactId>aggregator-microservices</artifactId>
+		<artifactId>aggregator-microservices</artifactId>
-        <groupId>com.iluwatar</groupId>
+		<groupId>com.iluwatar</groupId>
-        <version>1.22.0-SNAPSHOT</version>
+		<version>1.23.0-SNAPSHOT</version>
-    </parent>
+	</parent>
-    <modelVersion>4.0.0</modelVersion>
+	<modelVersion>4.0.0</modelVersion>
-    <artifactId>aggregator-service</artifactId>
+	<artifactId>aggregator-service</artifactId>
-    <packaging>jar</packaging>
+	<packaging>jar</packaging>
-    <dependencies>
+	<dependencies>
-        <dependency>
+		<dependency>
-            <groupId>org.springframework</groupId>
+			<groupId>org.springframework</groupId>
-            <artifactId>spring-webmvc</artifactId>
+			<artifactId>spring-webmvc</artifactId>
-        </dependency>
+		</dependency>
-        <dependency>
+		<dependency>
-            <groupId>org.springframework.boot</groupId>
+			<groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-web</artifactId>
+			<artifactId>spring-boot-starter-web</artifactId>
-        </dependency>
+		</dependency>
-        <dependency>
+		<dependency>
-            <groupId>org.junit.jupiter</groupId>
+			<groupId>org.junit.jupiter</groupId>
-            <artifactId>junit-jupiter-engine</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-            <scope>test</scope>
+			<scope>test</scope>
-        </dependency>
+		</dependency>
-        <dependency>
+		<dependency>
-            <groupId>org.mockito</groupId>
+			<groupId>org.mockito</groupId>
-            <artifactId>mockito-core</artifactId>
+			<artifactId>mockito-core</artifactId>
-            <scope>test</scope>
+			<scope>test</scope>
-        </dependency>
+		</dependency>
-    </dependencies>
+	</dependencies>
 
-    <build>
+	<build>
-        <plugins>
+		<plugins>
-            <plugin>
+			<plugin>
-                <groupId>org.springframework.boot</groupId>
+				<groupId>org.springframework.boot</groupId>
-                <artifactId>spring-boot-maven-plugin</artifactId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
-                <executions>
+				<executions>
-                    <execution>
+					<execution>
-                        <goals>
+						<goals>
-                            <goal>repackage</goal>
+							<goal>repackage</goal>
-                        </goals>
+						</goals>
-                    </execution>
+					</execution>
-                </executions>
+				</executions>
-            </plugin>
+			</plugin>
-        </plugins>
+			<!-- Maven assembly plugin is invoked with default setting which we have 
-    </build>
+				in parent pom and specifying the class having main method -->
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.aggregator.microservices.App</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

aggregator-microservices/etc/aggregator-microservices.urm.puml

@@ -0,0 +1,2 @@
+@startuml
+@enduml

aggregator-microservices/information-microservice/etc/information-microservice.urm.puml

@@ -0,0 +1,12 @@
+@startuml
+package com.iluwatar.information.microservice {
+  class InformationApplication {
+    + InformationApplication()
+    + main(args : String[]) {static}
+  }
+  class InformationController {
+    + InformationController()
+    + getProductTitle() : String
+  }
+}
+@enduml

aggregator-microservices/information-microservice/pom.xml

@@ -1,70 +1,76 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN 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.
-
--->
 <project xmlns="http://maven.apache.org/POM/4.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <parent>
+	<parent>
-        <artifactId>aggregator-microservices</artifactId>
+		<artifactId>aggregator-microservices</artifactId>
-        <groupId>com.iluwatar</groupId>
+		<groupId>com.iluwatar</groupId>
-        <version>1.22.0-SNAPSHOT</version>
+		<version>1.23.0-SNAPSHOT</version>
-    </parent>
+	</parent>
-    <modelVersion>4.0.0</modelVersion>
+	<modelVersion>4.0.0</modelVersion>
 
-    <artifactId>information-microservice</artifactId>
+	<artifactId>information-microservice</artifactId>
-    <packaging>jar</packaging>
+	<packaging>jar</packaging>
 
-    <dependencies>
+	<dependencies>
-        <dependency>
+		<dependency>
-            <groupId>org.springframework</groupId>
+			<groupId>org.springframework</groupId>
-            <artifactId>spring-webmvc</artifactId>
+			<artifactId>spring-webmvc</artifactId>
-        </dependency>
+		</dependency>
-        <dependency>
+		<dependency>
-            <groupId>org.springframework.boot</groupId>
+			<groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-web</artifactId>
+			<artifactId>spring-boot-starter-web</artifactId>
-        </dependency>
+		</dependency>
-        <dependency>
+		<dependency>
-            <groupId>org.junit.jupiter</groupId>
+			<groupId>org.junit.jupiter</groupId>
-            <artifactId>junit-jupiter-engine</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-            <scope>test</scope>
+			<scope>test</scope>
-        </dependency>
+		</dependency>
-    </dependencies>
+	</dependencies>
 
-    <build>
+	<build>
-        <plugins>
+		<plugins>
-            <plugin>
+			<plugin>
-                <groupId>org.springframework.boot</groupId>
+				<groupId>org.springframework.boot</groupId>
-                <artifactId>spring-boot-maven-plugin</artifactId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
-                <executions>
+				<executions>
-                    <execution>
+					<execution>
-                        <goals>
+						<goals>
-                            <goal>repackage</goal>
+							<goal>repackage</goal>
-                        </goals>
+						</goals>
-                    </execution>
+					</execution>
-                </executions>
+				</executions>
-            </plugin>
+			</plugin>
-        </plugins>
+			<plugin>
-    </build>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.information.microservices.InformationApplication</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

aggregator-microservices/inventory-microservice/etc/inventory-microservice.urm.puml

@@ -0,0 +1,12 @@
+@startuml
+package com.iluwatar.inventory.microservice {
+  class InventoryApplication {
+    + InventoryApplication()
+    + main(args : String[]) {static}
+  }
+  class InventoryController {
+    + InventoryController()
+    + getProductInventories() : int
+  }
+}
+@enduml

aggregator-microservices/inventory-microservice/pom.xml

@@ -1,69 +1,75 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN 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.
-
--->
 <project xmlns="http://maven.apache.org/POM/4.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <parent>
+	<parent>
-        <artifactId>aggregator-microservices</artifactId>
+		<artifactId>aggregator-microservices</artifactId>
-        <groupId>com.iluwatar</groupId>
+		<groupId>com.iluwatar</groupId>
-        <version>1.22.0-SNAPSHOT</version>
+		<version>1.23.0-SNAPSHOT</version>
-    </parent>
+	</parent>
-    <modelVersion>4.0.0</modelVersion>
+	<modelVersion>4.0.0</modelVersion>
-    <artifactId>inventory-microservice</artifactId>
+	<artifactId>inventory-microservice</artifactId>
 
-    <packaging>jar</packaging>
+	<packaging>jar</packaging>
-    <dependencies>
+	<dependencies>
-        <dependency>
+		<dependency>
-            <groupId>org.springframework</groupId>
+			<groupId>org.springframework</groupId>
-            <artifactId>spring-webmvc</artifactId>
+			<artifactId>spring-webmvc</artifactId>
-        </dependency>
+		</dependency>
-        <dependency>
+		<dependency>
-            <groupId>org.springframework.boot</groupId>
+			<groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-web</artifactId>
+			<artifactId>spring-boot-starter-web</artifactId>
-        </dependency>
+		</dependency>
-        <dependency>
+		<dependency>
-            <groupId>org.junit.jupiter</groupId>
+			<groupId>org.junit.jupiter</groupId>
-            <artifactId>junit-jupiter-engine</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-            <scope>test</scope>
+			<scope>test</scope>
-        </dependency>
+		</dependency>
-    </dependencies>
+	</dependencies>
 
-    <build>
+	<build>
-        <plugins>
+		<plugins>
-            <plugin>
+			<plugin>
-                <groupId>org.springframework.boot</groupId>
+				<groupId>org.springframework.boot</groupId>
-                <artifactId>spring-boot-maven-plugin</artifactId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
-                <executions>
+				<executions>
-                    <execution>
+					<execution>
-                        <goals>
+						<goals>
-                            <goal>repackage</goal>
+							<goal>repackage</goal>
-                        </goals>
+						</goals>
-                    </execution>
+					</execution>
-                </executions>
+				</executions>
-            </plugin>
+			</plugin>
-        </plugins>
+			<plugin>
-    </build>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.inventory.microservices.InventoryApplication</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

aggregator-microservices/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.22.0-SNAPSHOT</version>
+        <version>1.23.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
     <artifactId>aggregator-microservices</artifactId>

ambassador/README.md

@@ -5,8 +5,8 @@ folder: ambassador
 permalink: /patterns/ambassador/
 categories: Structural
 tags:
- - Java
+  - Decoupling
- - Difficulty-Intermediate
+  - Cloud distributed
 ---
 
 ## Intent
@@ -23,8 +23,7 @@ In plain words
 
 Microsoft documentation states
 
-> An ambassador service can be thought of as an out-of-process proxy that is co-located with the client.
+> An ambassador service can be thought of as an out-of-process proxy that is co-located with the client. This pattern can be useful for offloading common client connectivity tasks such as monitoring, logging, routing, security (such as TLS), and resiliency patterns in a language agnostic way. It is often used with legacy applications, or other applications that are difficult to modify, in order to extend their networking capabilities. It can also enable a specialized team to implement those features.
-  This pattern can be useful for offloading common client connectivity tasks such as monitoring, logging, routing, security (such as TLS), and resiliency patterns in a language agnostic way. It is often used with legacy applications, or other applications that are difficult to modify, in order to extend their networking capabilities. It can also enable a specialized team to implement those features.
 
 **Programmatic Example**
 
@@ -150,6 +149,9 @@ public class App {
 }
 ```
 
+## Class diagram
+![alt text](./etc/ambassador.urm.png "Ambassador class diagram")
+
 ## Applicability
 Ambassador is applicable when working with a legacy remote service that cannot
 be modified or would be extremely difficult to modify. Connectivity features can

ambassador/etc/ambassador.urm.puml

@@ -0,0 +1,47 @@
+@startuml
+package com.iluwatar.ambassador.util {
+  interface RandomProvider {
+    + random() : double {abstract}
+  }
+}
+package com.iluwatar.ambassador {
+  class App {
+    + App()
+    + main(args : String[]) {static}
+  }
+  class Client {
+    - LOGGER : Logger {static}
+    - serviceAmbassador : ServiceAmbassador
+    + Client()
+    ~ useService(value : int) : long
+  }
+  class RemoteService {
+    - LOGGER : Logger {static}
+    - THRESHOLD : int {static}
+    - randomProvider : RandomProvider
+    - service : RemoteService {static}
+    - RemoteService()
+    ~ RemoteService(randomProvider : RandomProvider)
+    + doRemoteFunction(value : int) : long
+    ~ getRemoteService() : RemoteService {static}
+  }
+  ~interface RemoteServiceInterface {
+    + FAILURE : int {static}
+    + doRemoteFunction(int) : long {abstract}
+  }
+  class ServiceAmbassador {
+    - DELAY_MS : int {static}
+    - LOGGER : Logger {static}
+    - RETRIES : int {static}
+    ~ ServiceAmbassador()
+    - checkLatency(value : int) : long
+    + doRemoteFunction(value : int) : long
+    - safeCall(value : int) : long
+  }
+}
+RemoteService -->  "-service" RemoteService
+Client -->  "-serviceAmbassador" ServiceAmbassador
+RemoteService -->  "-randomProvider" RandomProvider
+RemoteService ..|> RemoteServiceInterface 
+ServiceAmbassador ..|> RemoteServiceInterface 
+@enduml

ambassador/pom.xml

@@ -1,43 +1,53 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN 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.
-
--->
 <project xmlns="http://maven.apache.org/POM/4.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-  <parent>
+	<parent>
-    <artifactId>java-design-patterns</artifactId>
+		<artifactId>java-design-patterns</artifactId>
-    <groupId>com.iluwatar</groupId>
+		<groupId>com.iluwatar</groupId>
-    <version>1.22.0-SNAPSHOT</version>
+		<version>1.23.0-SNAPSHOT</version>
-  </parent>
+	</parent>
-  <modelVersion>4.0.0</modelVersion>
+	<modelVersion>4.0.0</modelVersion>
-  <artifactId>ambassador</artifactId>
+	<artifactId>ambassador</artifactId>
-  <dependencies>
+	<dependencies>
-    <dependency>
+		<dependency>
-      <groupId>org.junit.jupiter</groupId>
+			<groupId>org.junit.jupiter</groupId>
-      <artifactId>junit-jupiter-engine</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-      <scope>test</scope>
+			<scope>test</scope>
-    </dependency>
+		</dependency>
-  </dependencies>
+	</dependencies>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.ambassador.App</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

api-gateway/README.md

@@ -5,26 +5,155 @@ folder: api-gateway
 permalink: /patterns/api-gateway/
 categories: Architectural
 tags:
-- Java
+  - Cloud distributed
-- Difficulty-Intermediate
+  - Decoupling
-- Spring
+  - Microservices
 ---
 
 ## Intent
 
-Aggregate calls to microservices in a single location: the API Gateway. The user makes a single
+Aggregate calls to microservices in a single location: the API Gateway. The user makes a single call to the API Gateway, 
-call to the API Gateway, and the API Gateway then calls each relevant microservice.
+and the API Gateway then calls each relevant microservice.
 
+## Explanation
+
+With the Microservices pattern, a client may need data from multiple different microservices. If the client called each 
+microservice directly, that could contribute to longer load times, since the client would have to make a network request 
+for each microservice called. Moreover, having the client call each microservice directly ties the client to that 
+microservice - if the internal implementations of the microservices change (for example, if two microservices are 
+combined sometime in the future) or if the location (host and port) of a microservice changes, then every client that 
+makes use of those microservices must be updated.
+
+The intent of the API Gateway pattern is to alleviate some of these issues. In the API Gateway pattern, an additional 
+entity (the API Gateway) is placed between the client and the microservices. The job of the API Gateway is to aggregate 
+the calls to the microservices. Rather than the client calling each microservice individually, the client calls the 
+API Gateway a single time. The API Gateway then calls each of the microservices that the client needs.
+
+Real world example
+
+> We are implementing microservices and API Gateway pattern for an e-commerce site. In this system the API Gateway makes 
+calls to the Image and Price microservices.
+
+In plain words
+
+> For a system implemented using microservices architecture, API Gateway is the single entry point that aggregates the 
+calls to the individual microservices. 
+
+Wikipedia says
+
+> API Gateway is a server that acts as an API front-end, receives API requests, enforces throttling and security 
+policies, passes requests to the back-end service and then passes the response back to the requester. A gateway often 
+includes a transformation engine to orchestrate and modify the requests and responses on the fly. A gateway can also 
+provide functionality such as collecting analytics data and providing caching. The gateway can provide functionality to 
+support authentication, authorization, security, audit and regulatory compliance.
+
+**Programmatic Example**
+
+This implementation shows what the API Gateway pattern could look like for an e-commerce site. The `ApiGateway` makes 
+calls to the Image and Price microservices using the `ImageClientImpl` and `PriceClientImpl` respectively. Customers 
+viewing the site on a desktop device can see both price information and an image of a product, so the `ApiGateway` calls 
+both of the microservices and aggregates the data in the `DesktopProduct` model. However, mobile users only see price 
+information; they do not see a product image. For mobile users, the `ApiGateway` only retrieves price information, which 
+it uses to populate the `MobileProduct`.
+
+Here's the Image microservice implementation.
+
+```java
+public interface ImageClient {
+  String getImagePath();
+}
+
+public class ImageClientImpl implements ImageClient {
+
+  @Override
+  public String getImagePath() {
+    var httpClient = HttpClient.newHttpClient();
+    var httpGet = HttpRequest.newBuilder()
+        .GET()
+        .uri(URI.create("http://localhost:50005/image-path"))
+        .build();
+
+    try {
+      var httpResponse = httpClient.send(httpGet, BodyHandlers.ofString());
+      return httpResponse.body();
+    } catch (IOException | InterruptedException e) {
+      e.printStackTrace();
+    }
+
+    return null;
+  }
+}
+```
+
+Here's the Price microservice implementation.
+
+```java
+public interface PriceClient {
+  String getPrice();
+}
+
+public class PriceClientImpl implements PriceClient {
+
+  @Override
+  public String getPrice() {
+    var httpClient = HttpClient.newHttpClient();
+    var httpGet = HttpRequest.newBuilder()
+        .GET()
+        .uri(URI.create("http://localhost:50006/price"))
+        .build();
+
+    try {
+      var httpResponse = httpClient.send(httpGet, BodyHandlers.ofString());
+      return httpResponse.body();
+    } catch (IOException | InterruptedException e) {
+      e.printStackTrace();
+    }
+
+    return null;
+  }
+}
+```
+
+And here we can see how API Gateway maps the requests to the microservices.
+
+```java
+public class ApiGateway {
+
+  @Resource
+  private ImageClient imageClient;
+
+  @Resource
+  private PriceClient priceClient;
+
+  @RequestMapping(path = "/desktop", method = RequestMethod.GET)
+  public DesktopProduct getProductDesktop() {
+    var desktopProduct = new DesktopProduct();
+    desktopProduct.setImagePath(imageClient.getImagePath());
+    desktopProduct.setPrice(priceClient.getPrice());
+    return desktopProduct;
+  }
+
+  @RequestMapping(path = "/mobile", method = RequestMethod.GET)
+  public MobileProduct getProductMobile() {
+    var mobileProduct = new MobileProduct();
+    mobileProduct.setPrice(priceClient.getPrice());
+    return mobileProduct;
+  }
+}
+```
+
+## Class diagram
 ![alt text](./etc/api-gateway.png "API Gateway")
 
 ## Applicability
 
 Use the API Gateway pattern when
 
-* you're also using the Microservices pattern and need a single point of aggregation for your
+* You're using microservices architecture and need a single point of aggregation for your microservice calls.
-microservice calls
 
 ## Credits
 
 * [microservices.io - API Gateway](http://microservices.io/patterns/apigateway.html)
 * [NGINX - Building Microservices: Using an API Gateway](https://www.nginx.com/blog/building-microservices-using-an-api-gateway/)
+* [Microservices Patterns: With examples in Java](https://www.amazon.com/gp/product/1617294543/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=1617294543&linkId=ac7b6a57f866ac006a309d9086e8cfbd)
+* [Building Microservices: Designing Fine-Grained Systems](https://www.amazon.com/gp/product/1491950358/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=1491950358&linkId=4c95ca9831e05e3f0dadb08841d77bf1)

api-gateway/api-gateway-service/etc/api-gateway-service.urm.puml

@@ -0,0 +1,48 @@
+@startuml
+package com.iluwatar.api.gateway {
+  class ApiGateway {
+    - imageClient : ImageClient
+    - priceClient : PriceClient
+    + ApiGateway()
+    + getProductDesktop() : DesktopProduct
+    + getProductMobile() : MobileProduct
+  }
+  class App {
+    + App()
+    + main(args : String[]) {static}
+  }
+  class DesktopProduct {
+    - imagePath : String
+    - price : String
+    + DesktopProduct()
+    + getImagePath() : String
+    + getPrice() : String
+    + setImagePath(imagePath : String)
+    + setPrice(price : String)
+  }
+  interface ImageClient {
+    + getImagePath() : String {abstract}
+  }
+  class ImageClientImpl {
+    + ImageClientImpl()
+    + getImagePath() : String
+  }
+  class MobileProduct {
+    - price : String
+    + MobileProduct()
+    + getPrice() : String
+    + setPrice(price : String)
+  }
+  interface PriceClient {
+    + getPrice() : String {abstract}
+  }
+  class PriceClientImpl {
+    + PriceClientImpl()
+    + getPrice() : String
+  }
+}
+ApiGateway -->  "-imageClient" ImageClient
+ApiGateway -->  "-priceClient" PriceClient
+ImageClientImpl ..|> ImageClient 
+PriceClientImpl ..|> PriceClient 
+@enduml

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

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>api-gateway</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.22.0-SNAPSHOT</version>
+    <version>1.23.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>api-gateway-service</artifactId>
@@ -68,6 +68,21 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.api.gateway.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
     </plugins>
   </build>
 </project>

api-gateway/etc/api-gateway.urm.puml

@@ -0,0 +1,2 @@
+@startuml
+@enduml

api-gateway/image-microservice/etc/image-microservice.urm.puml

@@ -0,0 +1,12 @@
+@startuml
+package com.iluwatar.image.microservice {
+  class ImageApplication {
+    + ImageApplication()
+    + main(args : String[]) {static}
+  }
+  class ImageController {
+    + ImageController()
+    + getImagePath() : String
+  }
+}
+@enduml

api-gateway/image-microservice/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>api-gateway</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.22.0-SNAPSHOT</version>
+    <version>1.23.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>image-microservice</artifactId>
@@ -63,6 +63,21 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.image.microservice.ImageApplication</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
     </plugins>
   </build>
 </project>

api-gateway/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.22.0-SNAPSHOT</version>
+    <version>1.23.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>api-gateway</artifactId>

api-gateway/price-microservice/etc/price-microservice.urm.puml

@@ -0,0 +1,12 @@
+@startuml
+package com.iluwatar.price.microservice {
+  class PriceApplication {
+    + PriceApplication()
+    + main(args : String[]) {static}
+  }
+  class PriceController {
+    + PriceController()
+    + getPrice() : String
+  }
+}
+@enduml

api-gateway/price-microservice/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>api-gateway</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.22.0-SNAPSHOT</version>
+    <version>1.23.0-SNAPSHOT</version>
   </parent>
 
   <modelVersion>4.0.0</modelVersion>
@@ -65,6 +65,21 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.price.microservices.PriceApplication</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
     </plugins>
   </build>
 </project>

arrange-act-assert/README.md

@@ -0,0 +1,30 @@
+---
+layout: pattern
+title: Arrange/Act/Assert
+folder: arrange-act-assert
+permalink: /patterns/arrange-act-assert/
+categories: Idiom
+tags:
+ - Testing
+---
+
+## Also known as
+Given/When/Then
+
+## Intent
+The Arrange/Act/Assert (AAA) is a pattern for organizing unit tests.
+It breaks tests down into three clear and distinct steps:
+1. Arrange: Perform the setup and initialization required for the test.
+2. Act: Take action(s) required for the test.
+3. Assert: Verify the outcome(s) of the test.
+
+## Applicability
+Use Arrange/Act/Assert pattern when
+
+* you need to structure your unit tests so they're easier to read, maintain, and enhance. 
+
+## Credits
+
+* [Arrange, Act, Assert: What is AAA Testing?](https://blog.ncrunch.net/post/arrange-act-assert-aaa-testing.aspx)
+* [Bill Wake: 3A – Arrange, Act, Assert](https://xp123.com/articles/3a-arrange-act-assert/)
+* [Martin Fowler: GivenWhenThen](https://martinfowler.com/bliki/GivenWhenThen.html)

arrange-act-assert/etc/arrange-act-assert.urm.puml

@@ -0,0 +1,11 @@
+@startuml
+package com.iluwatar.arrangeactassert {
+  class Cash {
+    - amount : int
+    ~ Cash(amount : int)
+    ~ count() : int
+    ~ minus(subtrahend : int) : boolean
+    ~ plus(addend : int)
+  }
+}
+@enduml

arrange-act-assert/pom.xml

@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    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.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <parent>
+    <artifactId>java-design-patterns</artifactId>
+    <groupId>com.iluwatar</groupId>
+    <version>1.23.0-SNAPSHOT</version>
+  </parent>
+  <modelVersion>4.0.0</modelVersion>
+
+  <artifactId>arrange-act-assert</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>

arrange-act-assert/src/main/java/com/iluwatar/arrangeactassert/Cash.java

@@ -0,0 +1,57 @@
+/*
+ * 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.arrangeactassert;
+
+/**
+ * Arrange/Act/Assert (AAA) is a unit test pattern. In this simple example, we have a ({@link Cash})
+ * object for plus, minus and counting amount.
+ */
+public class Cash {
+
+  private int amount;
+
+  Cash(int amount) {
+    this.amount = amount;
+  }
+
+  //plus
+  void plus(int addend) {
+    amount += addend;
+  }
+
+  //minus
+  boolean minus(int subtrahend) {
+    if (amount >= subtrahend) {
+      amount -= subtrahend;
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  //count
+  int count() {
+    return amount;
+  }
+}

arrange-act-assert/src/test/java/com/iluwatar/arrangeactassert/CashAAATest.java

@@ -0,0 +1,99 @@
+/*
+ * 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.arrangeactassert;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+/**
+ * Arrange/Act/Assert (AAA) is a pattern for organizing unit tests. It is a way to structure your
+ * tests so they're easier to read, maintain and enhance.
+ *
+ * <p>It breaks tests down into three clear and distinct steps:
+ * <p>1. Arrange: Perform the setup and initialization required for the test.
+ * <p>2. Act: Take action(s) required for the test.
+ * <p>3. Assert: Verify the outcome(s) of the test.
+ *
+ * <p>This pattern has several significant benefits. It creates a clear separation between a test's
+ * setup, operations, and results. This structure makes the code easier to read and understand. If
+ * you place the steps in order and format your code to separate them, you can scan a test and
+ * quickly comprehend what it does.
+ *
+ * <p>It also enforces a certain degree of discipline when you write your tests. You have to think
+ * clearly about the three steps your test will perform. But it makes tests more natural to write at
+ * the same time since you already have an outline.
+ *
+ * <p>In ({@link CashAAATest}) we have four test methods. Each of them has only one reason to
+ * change and one reason to fail. In a large and complicated code base, tests that honor the single
+ * responsibility principle are much easier to troubleshoot.
+ */
+public class CashAAATest {
+
+  @Test
+  public void testPlus() {
+    //Arrange
+    var cash = new Cash(3);
+    //Act
+    cash.plus(4);
+    //Assert
+    assertEquals(cash.count(), 7);
+  }
+
+  @Test
+  public void testMinus() {
+    //Arrange
+    var cash = new Cash(8);
+    //Act
+    var result = cash.minus(5);
+    //Assert
+    assertTrue(result);
+    assertEquals(cash.count(), 3);
+  }
+
+  @Test
+  public void testInsufficientMinus() {
+    //Arrange
+    var cash = new Cash(1);
+    //Act
+    var result = cash.minus(6);
+    //Assert
+    assertFalse(result);
+    assertEquals(cash.count(), 1);
+  }
+
+  @Test
+  public void testUpdate() {
+    //Arrange
+    var cash = new Cash(5);
+    //Act
+    cash.plus(6);
+    var result = cash.minus(3);
+    //Assert
+    assertTrue(result);
+    assertEquals(cash.count(), 8);
+  }
+}

arrange-act-assert/src/test/java/com/iluwatar/arrangeactassert/CashAntiAAATest.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.arrangeactassert;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+/**
+ * ({@link CashAAATest}) is an anti-example of AAA pattern. This test is functionally correct, but
+ * with the addition of new feature, it needs refactoring. There are an awful lot of steps in that
+ * test method, but it verifies the class' important behavior in just eleven lines. It violates the
+ * single responsibility principle. If this test method failed after a small code change, it might
+ * take some digging to discover why.
+ */
+public class CashAntiAAATest {
+
+  @Test
+  public void testCash() {
+    //initialize
+    var cash = new Cash(3);
+    //test plus
+    cash.plus(4);
+    assertEquals(cash.count(), 7);
+    //test minus
+    cash = new Cash(8);
+    assertTrue(cash.minus(5));
+    assertEquals(cash.count(), 3);
+    assertFalse(cash.minus(6));
+    assertEquals(cash.count(), 3);
+    //test update
+    cash.plus(5);
+    assertTrue(cash.minus(5));
+    assertEquals(cash.count(), 3);
+  }
+}

async-method-invocation/README.md

@@ -5,9 +5,6 @@ folder: async-method-invocation
 permalink: /patterns/async-method-invocation/
 categories: Concurrency
 tags:
- - Java
- - Difficulty-Intermediate
- - Functional
  - Reactive
 ---
 
@@ -17,6 +14,7 @@ is not blocked while waiting results of tasks. The pattern provides parallel
 processing of multiple independent tasks and retrieving the results via
 callbacks or waiting until everything is done. 
 
+# Class diagram
 ![alt text](./etc/async-method-invocation.png "Async Method Invocation")
 
 ## Applicability

async-method-invocation/etc/async-method-invocation.urm.puml

@@ -0,0 +1,51 @@
+@startuml
+package com.iluwatar.async.method.invocation {
+  class App {
+    - LOGGER : Logger {static}
+    + App()
+    - callback(name : String) : AsyncCallback<T> {static}
+    - lazyval(value : T, delayMillis : long) : Callable<T> {static}
+    - log(msg : String) {static}
+    + main(args : String[]) {static}
+  }
+  interface AsyncCallback<T> {
+    + onComplete(T, Optional<Exception>) {abstract}
+  }
+  interface AsyncExecutor {
+    + endProcess(AsyncResult<T>) : T {abstract}
+    + startProcess(Callable<T>) : AsyncResult<T> {abstract}
+    + startProcess(Callable<T>, AsyncCallback<T>) : AsyncResult<T> {abstract}
+  }
+  interface AsyncResult<T> {
+    + await() {abstract}
+    + getValue() : T {abstract}
+    + isCompleted() : boolean {abstract}
+  }
+  class ThreadAsyncExecutor {
+    - idx : AtomicInteger
+    + ThreadAsyncExecutor()
+    + endProcess(asyncResult : AsyncResult<T>) : T
+    + startProcess(task : Callable<T>) : AsyncResult<T>
+    + startProcess(task : Callable<T>, callback : AsyncCallback<T>) : AsyncResult<T>
+  }
+  -class CompletableResult<T> {
+    ~ COMPLETED : int {static}
+    ~ FAILED : int {static}
+    ~ RUNNING : int {static}
+    ~ callback : Optional<AsyncCallback<T>>
+    ~ exception : Exception
+    ~ lock : Object
+    ~ state : int
+    ~ value : T
+    ~ CompletableResult<T>(callback : AsyncCallback<T>)
+    + await()
+    + getValue() : T
+    + isCompleted() : boolean
+    ~ setException(exception : Exception)
+    ~ setValue(value : T)
+  }
+}
+CompletableResult ..+ ThreadAsyncExecutor
+ThreadAsyncExecutor ..|> AsyncExecutor 
+CompletableResult ..|> AsyncResult 
+@enduml

async-method-invocation/pom.xml

@@ -1,52 +1,64 @@
 <?xml version="1.0"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN THE SOFTWARE. -->
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+<project
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	xmlns="http://maven.apache.org/POM/4.0.0"
-    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	<modelVersion>4.0.0</modelVersion>
-    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+	<parent>
-    THE SOFTWARE.
+		<groupId>com.iluwatar</groupId>
-
+		<artifactId>java-design-patterns</artifactId>
--->
+		<version>1.23.0-SNAPSHOT</version>
-<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+	</parent>
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+	<artifactId>async-method-invocation</artifactId>
-  <modelVersion>4.0.0</modelVersion>
+	<dependencies>
-  <parent>
+		<dependency>
-    <groupId>com.iluwatar</groupId>
+			<groupId>org.junit.jupiter</groupId>
-    <artifactId>java-design-patterns</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-    <version>1.22.0-SNAPSHOT</version>
+			<scope>test</scope>
-  </parent>
+		</dependency>
-  <artifactId>async-method-invocation</artifactId>
+		<dependency>
-  <dependencies>
+			<groupId>org.mockito</groupId>
-    <dependency>
+			<artifactId>mockito-core</artifactId>
-      <groupId>org.junit.jupiter</groupId>
+			<scope>test</scope>
-      <artifactId>junit-jupiter-engine</artifactId>
+		</dependency>
-      <scope>test</scope>
+		<dependency>
-    </dependency>
+			<groupId>junit</groupId>
-    <dependency>
+			<artifactId>junit</artifactId>
-      <groupId>org.mockito</groupId>
+			<scope>test</scope>
-      <artifactId>mockito-core</artifactId>
+		</dependency>
-      <scope>test</scope>
+	</dependencies>
-    </dependency>
+	<build>
-    <dependency>
+		<plugins>
-      <groupId>junit</groupId>
+			<plugin>
-      <artifactId>junit</artifactId>
+				<groupId>org.apache.maven.plugins</groupId>
-      <scope>test</scope>
+				<artifactId>maven-assembly-plugin</artifactId>
-    </dependency>
+				<executions>
-  </dependencies>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.async.method.invocation.App</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

balking/README.md

@@ -5,14 +5,14 @@ folder: balking
 permalink: /patterns/balking/
 categories: Concurrency
 tags:
- - Java
+ - Decoupling
- - Difficulty-Beginner
 ---
 
 ## Intent
 Balking Pattern is used to prevent an object from executing certain code if it is an
 incomplete or inappropriate state
 
+## Class diagram
 ![alt text](./etc/balking.png "Balking")
 
 ## Applicability

balking/etc/balking.urm.puml

@@ -0,0 +1,30 @@
+@startuml
+package com.iluwatar.balking {
+  class App {
+    - LOGGER : Logger {static}
+    + App()
+    + main(args : String[]) {static}
+  }
+  interface DelayProvider {
+    + executeAfterDelay(long, TimeUnit, Runnable) {abstract}
+  }
+  class WashingMachine {
+    - LOGGER : Logger {static}
+    - delayProvider : DelayProvider
+    - washingMachineState : WashingMachineState
+    + WashingMachine()
+    + WashingMachine(delayProvider : DelayProvider)
+    + endOfWashing()
+    + getWashingMachineState() : WashingMachineState
+    + wash()
+  }
+  enum WashingMachineState {
+    + ENABLED {static}
+    + WASHING {static}
+    + valueOf(name : String) : WashingMachineState {static}
+    + values() : WashingMachineState[] {static}
+  }
+}
+WashingMachine -->  "-washingMachineState" WashingMachineState
+WashingMachine -->  "-delayProvider" DelayProvider
+@enduml

balking/pom.xml

@@ -1,46 +1,54 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN 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.
-
--->
 <project xmlns="http://maven.apache.org/POM/4.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-  <parent>
+	<parent>
-    <artifactId>java-design-patterns</artifactId>
+		<artifactId>java-design-patterns</artifactId>
-    <groupId>com.iluwatar</groupId>
+		<groupId>com.iluwatar</groupId>
-    <version>1.22.0-SNAPSHOT</version>
+		<version>1.23.0-SNAPSHOT</version>
-  </parent>
+	</parent>
-  <modelVersion>4.0.0</modelVersion>
+	<modelVersion>4.0.0</modelVersion>
-
-  <artifactId>balking</artifactId>
-  <dependencies>
-    <dependency>
-      <groupId>org.junit.jupiter</groupId>
-      <artifactId>junit-jupiter-engine</artifactId>
-      <scope>test</scope>
-    </dependency>
-  </dependencies>
-
 
+	<artifactId>balking</artifactId>
+	<dependencies>
+		<dependency>
+			<groupId>org.junit.jupiter</groupId>
+			<artifactId>junit-jupiter-engine</artifactId>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.balking.App</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

bridge/README.md

@@ -5,9 +5,7 @@ folder: bridge
 permalink: /patterns/bridge/
 categories: Structural
 tags:
- - Java
+ - Gang of Four
- - Gang Of Four
- - Difficulty-Intermediate
 ---
 
 ## Also known as
@@ -179,6 +177,9 @@ hammer.unwield();
 // The item's glow fades.
 ```
 
+## Class diagram
+![alt text](./etc/bridge.urm.png "Bridge class diagram")
+
 ## Applicability
 Use the Bridge pattern when
 
@@ -193,4 +194,5 @@ Use the Bridge pattern when
 
 ## Credits
 
-* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://www.amazon.com/gp/product/0201633612/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0201633612&linkCode=as2&tag=javadesignpat-20&linkId=675d49790ce11db99d90bde47f1aeb59)
+* [Head First Design Patterns: A Brain-Friendly Guide](https://www.amazon.com/gp/product/0596007124/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596007124&linkCode=as2&tag=javadesignpat-20&linkId=6b8b6eea86021af6c8e3cd3fc382cb5b)

bridge/etc/bridge.urm.puml

@@ -0,0 +1,58 @@
+@startuml
+package com.iluwatar.bridge {
+  class App {
+    - LOGGER : Logger {static}
+    + App()
+    + main(args : String[]) {static}
+  }
+  interface Enchantment {
+    + apply() {abstract}
+    + onActivate() {abstract}
+    + onDeactivate() {abstract}
+  }
+  class FlyingEnchantment {
+    - LOGGER : Logger {static}
+    + FlyingEnchantment()
+    + apply()
+    + onActivate()
+    + onDeactivate()
+  }
+  class Hammer {
+    - LOGGER : Logger {static}
+    - enchantment : Enchantment
+    + Hammer(enchantment : Enchantment)
+    + getEnchantment() : Enchantment
+    + swing()
+    + unwield()
+    + wield()
+  }
+  class SoulEatingEnchantment {
+    - LOGGER : Logger {static}
+    + SoulEatingEnchantment()
+    + apply()
+    + onActivate()
+    + onDeactivate()
+  }
+  class Sword {
+    - LOGGER : Logger {static}
+    - enchantment : Enchantment
+    + Sword(enchantment : Enchantment)
+    + getEnchantment() : Enchantment
+    + swing()
+    + unwield()
+    + wield()
+  }
+  interface Weapon {
+    + getEnchantment() : Enchantment {abstract}
+    + swing() {abstract}
+    + unwield() {abstract}
+    + wield() {abstract}
+  }
+}
+Sword -->  "-enchantment" Enchantment
+Hammer -->  "-enchantment" Enchantment
+FlyingEnchantment ..|> Enchantment 
+Hammer ..|> Weapon 
+SoulEatingEnchantment ..|> Enchantment 
+Sword ..|> Weapon 
+@enduml

bridge/pom.xml

@@ -1,47 +1,59 @@
 <?xml version="1.0"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN THE SOFTWARE. -->
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+<project
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	xmlns="http://maven.apache.org/POM/4.0.0"
-    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	<modelVersion>4.0.0</modelVersion>
-    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+	<parent>
-    THE SOFTWARE.
+		<groupId>com.iluwatar</groupId>
-
+		<artifactId>java-design-patterns</artifactId>
--->
+		<version>1.23.0-SNAPSHOT</version>
-<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+	</parent>
-    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+	<artifactId>bridge</artifactId>
-  <modelVersion>4.0.0</modelVersion>
+	<dependencies>
-  <parent>
+		<dependency>
-    <groupId>com.iluwatar</groupId>
+			<groupId>org.junit.jupiter</groupId>
-    <artifactId>java-design-patterns</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-    <version>1.22.0-SNAPSHOT</version>
+			<scope>test</scope>
-  </parent>
+		</dependency>
-  <artifactId>bridge</artifactId>
+		<dependency>
-  <dependencies>
+			<groupId>org.mockito</groupId>
-    <dependency>
+			<artifactId>mockito-core</artifactId>
-      <groupId>org.junit.jupiter</groupId>
+			<scope>test</scope>
-      <artifactId>junit-jupiter-engine</artifactId>
+		</dependency>
-      <scope>test</scope>
+	</dependencies>
-    </dependency>
+	<build>
-    <dependency>
+    <plugins>
-      <groupId>org.mockito</groupId>
+      <plugin>
-      <artifactId>mockito-core</artifactId>
+        <groupId>org.apache.maven.plugins</groupId>
-      <scope>test</scope>
+        <artifactId>maven-assembly-plugin</artifactId>
-    </dependency>
+        <executions>
-  </dependencies>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.bridge.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
 </project>

builder/README.md

@@ -5,9 +5,7 @@ folder: builder
 permalink: /patterns/builder/
 categories: Creational
 tags:
- - Java
+ - Gang of Four
- - Gang Of Four
- - Difficulty-Intermediate
 ---
 
 ## Intent
@@ -113,6 +111,9 @@ And then it can be used as:
 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
 
@@ -130,5 +131,7 @@ Use the Builder pattern when
 
 ## Credits
 
-* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://www.amazon.com/gp/product/0201633612/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0201633612&linkCode=as2&tag=javadesignpat-20&linkId=675d49790ce11db99d90bde47f1aeb59)
-* [Effective Java (2nd Edition)](http://www.amazon.com/Effective-Java-Edition-Joshua-Bloch/dp/0321356683)
+* [Effective Java](https://www.amazon.com/gp/product/0134685997/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0134685997&linkCode=as2&tag=javadesignpat-20&linkId=4e349f4b3ff8c50123f8147c828e53eb)
+* [Head First Design Patterns: A Brain-Friendly Guide](https://www.amazon.com/gp/product/0596007124/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596007124&linkCode=as2&tag=javadesignpat-20&linkId=6b8b6eea86021af6c8e3cd3fc382cb5b)
+* [Refactoring to Patterns](https://www.amazon.com/gp/product/0321213351/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0321213351&linkCode=as2&tag=javadesignpat-20&linkId=2a76fcb387234bc71b1c61150b3cc3a7)

builder/etc/builder.urm.puml

@@ -0,0 +1,100 @@
+@startuml
+package com.iluwatar.builder {
+  class App {
+    - LOGGER : Logger {static}
+    + App()
+    + main(args : String[]) {static}
+  }
+  enum Armor {
+    + CHAIN_MAIL {static}
+    + CLOTHES {static}
+    + LEATHER {static}
+    + PLATE_MAIL {static}
+    - title : String
+    + toString() : String
+    + valueOf(name : String) : Armor {static}
+    + values() : Armor[] {static}
+  }
+  enum HairColor {
+    + BLACK {static}
+    + BLOND {static}
+    + BROWN {static}
+    + RED {static}
+    + WHITE {static}
+    + toString() : String
+    + valueOf(name : String) : HairColor {static}
+    + values() : HairColor[] {static}
+  }
+  enum HairType {
+    + BALD {static}
+    + CURLY {static}
+    + LONG_CURLY {static}
+    + LONG_STRAIGHT {static}
+    + SHORT {static}
+    - title : String
+    + toString() : String
+    + valueOf(name : String) : HairType {static}
+    + values() : HairType[] {static}
+  }
+  class Hero {
+    - armor : Armor
+    - hairColor : HairColor
+    - hairType : HairType
+    - name : String
+    - profession : Profession
+    - weapon : Weapon
+    - Hero(builder : Builder)
+    + getArmor() : Armor
+    + getHairColor() : HairColor
+    + getHairType() : HairType
+    + getName() : String
+    + getProfession() : Profession
+    + getWeapon() : Weapon
+    + toString() : String
+  }
+  class Builder {
+    - armor : Armor
+    - hairColor : HairColor
+    - hairType : HairType
+    - name : String
+    - profession : Profession
+    - weapon : Weapon
+    + Builder(profession : Profession, name : String)
+    + build() : Hero
+    + withArmor(armor : Armor) : Builder
+    + withHairColor(hairColor : HairColor) : Builder
+    + withHairType(hairType : HairType) : Builder
+    + withWeapon(weapon : Weapon) : Builder
+  }
+  enum Profession {
+    + MAGE {static}
+    + PRIEST {static}
+    + THIEF {static}
+    + WARRIOR {static}
+    + toString() : String
+    + valueOf(name : String) : Profession {static}
+    + values() : Profession[] {static}
+  }
+  enum Weapon {
+    + AXE {static}
+    + BOW {static}
+    + DAGGER {static}
+    + SWORD {static}
+    + WARHAMMER {static}
+    + toString() : String
+    + valueOf(name : String) : Weapon {static}
+    + values() : Weapon[] {static}
+  }
+}
+Hero -->  "-profession" Profession
+Builder ..+ Hero
+Hero -->  "-armor" Armor
+Builder -->  "-hairColor" HairColor
+Builder -->  "-weapon" Weapon
+Builder -->  "-hairType" HairType
+Hero -->  "-hairColor" HairColor
+Builder -->  "-profession" Profession
+Hero -->  "-weapon" Weapon
+Hero -->  "-hairType" HairType
+Builder -->  "-armor" Armor
+@enduml

builder/pom.xml

@@ -1,42 +1,54 @@
 <?xml version="1.0"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN THE SOFTWARE. -->
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+<project
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	xmlns="http://maven.apache.org/POM/4.0.0"
-    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	<modelVersion>4.0.0</modelVersion>
-    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+	<parent>
-    THE SOFTWARE.
+		<groupId>com.iluwatar</groupId>
-
+		<artifactId>java-design-patterns</artifactId>
--->
+		<version>1.23.0-SNAPSHOT</version>
-<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+	</parent>
-    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+	<artifactId>builder</artifactId>
-  <modelVersion>4.0.0</modelVersion>
+	<dependencies>
-  <parent>
+		<dependency>
-    <groupId>com.iluwatar</groupId>
+			<groupId>org.junit.jupiter</groupId>
-    <artifactId>java-design-patterns</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-    <version>1.22.0-SNAPSHOT</version>
+			<scope>test</scope>
-  </parent>
+		</dependency>
-  <artifactId>builder</artifactId>
+	</dependencies>
-  <dependencies>
+	<build>
-    <dependency>
+    <plugins>
-      <groupId>org.junit.jupiter</groupId>
+      <plugin>
-      <artifactId>junit-jupiter-engine</artifactId>
+        <groupId>org.apache.maven.plugins</groupId>
-      <scope>test</scope>
+        <artifactId>maven-assembly-plugin</artifactId>
-    </dependency>
+        <executions>
-  </dependencies>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.builder.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
 </project>

business-delegate/README.md

@@ -3,10 +3,9 @@ layout: pattern
 title: Business Delegate
 folder: business-delegate
 permalink: /patterns/business-delegate/
-categories: Business Tier
+categories: Structural
 tags:
- - Java
+ - Decoupling
- - Difficulty-Intermediate
 ---
 
 ## Intent
@@ -15,6 +14,7 @@ presentation and business tiers. By using the pattern we gain loose coupling
 between the tiers and encapsulate knowledge about how to locate, connect to,
 and interact with the business objects that make up the application.
 
+## Class diagram
 ![alt text](./etc/business-delegate.png "Business Delegate")
 
 ## Applicability
@@ -26,4 +26,4 @@ Use the Business Delegate pattern when
 
 ## Credits
 
-* [J2EE Design Patterns](http://www.amazon.com/J2EE-Design-Patterns-William-Crawford/dp/0596004273/ref=sr_1_2)
+* [J2EE Design Patterns](https://www.amazon.com/gp/product/0596004273/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596004273&linkCode=as2&tag=javadesignpat-20&linkId=48d37c67fb3d845b802fa9b619ad8f31)

business-delegate/etc/business-delegate.urm.puml

@@ -0,0 +1,57 @@
+@startuml
+package com.iluwatar.business.delegate {
+  class App {
+    + App()
+    + main(args : String[]) {static}
+  }
+  class BusinessDelegate {
+    - businessService : BusinessService
+    - lookupService : BusinessLookup
+    - serviceType : ServiceType
+    + BusinessDelegate()
+    + doTask()
+    + setLookupService(businessLookup : BusinessLookup)
+    + setServiceType(serviceType : ServiceType)
+  }
+  class BusinessLookup {
+    - ejbService : EjbService
+    - jmsService : JmsService
+    + BusinessLookup()
+    + getBusinessService(serviceType : ServiceType) : BusinessService
+    + setEjbService(ejbService : EjbService)
+    + setJmsService(jmsService : JmsService)
+  }
+  interface BusinessService {
+    + doProcessing() {abstract}
+  }
+  class Client {
+    - businessDelegate : BusinessDelegate
+    + Client(businessDelegate : BusinessDelegate)
+    + doTask()
+  }
+  class EjbService {
+    - LOGGER : Logger {static}
+    + EjbService()
+    + doProcessing()
+  }
+  class JmsService {
+    - LOGGER : Logger {static}
+    + JmsService()
+    + doProcessing()
+  }
+  enum ServiceType {
+    + EJB {static}
+    + JMS {static}
+    + valueOf(name : String) : ServiceType {static}
+    + values() : ServiceType[] {static}
+  }
+}
+BusinessLookup -->  "-ejbService" EjbService
+BusinessDelegate -->  "-serviceType" ServiceType
+Client -->  "-businessDelegate" BusinessDelegate
+BusinessDelegate -->  "-businessService" BusinessService
+BusinessDelegate -->  "-lookupService" BusinessLookup
+BusinessLookup -->  "-jmsService" JmsService
+EjbService ..|> BusinessService 
+JmsService ..|> BusinessService 
+@enduml

business-delegate/pom.xml

@@ -1,36 +1,28 @@
 <?xml version="1.0"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN 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.
-
--->
 <project
 	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+	xmlns="http://maven.apache.org/POM/4.0.0"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 	<modelVersion>4.0.0</modelVersion>
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.22.0-SNAPSHOT</version>
+		<version>1.23.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>business-delegate</artifactId>
 	<dependencies>
@@ -45,4 +37,23 @@
 			<scope>test</scope>
 		</dependency>
 	</dependencies>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.business.delegate.App</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 </project>

business-delegate/src/main/java/com/iluwatar/business/delegate/module-info.java

@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */
+
+module com.iluwatar.business.delegate {
+	requires org.slf4j;
+}

bytecode/README.md

@@ -5,13 +5,15 @@ folder: bytecode
 permalink: /patterns/bytecode/
 categories: Behavioral
 tags:
- - Java
+ - Game programming
- - Difficulty-Beginner
 ---
 
 ## Intent
 Allows to encode behaviour as instructions for virtual machine.
 
+## Class diagram
+![alt text](./etc/bytecode.urm.png "Bytecode class diagram")
+
 ## Applicability
 Use the Bytecode pattern when you have a lot of behavior you need to define and your
 game’s implementation language isn’t a good fit because:

bytecode/etc/bytecode.urm.puml

@@ -0,0 +1,69 @@
+@startuml
+package com.iluwatar.bytecode {
+  class App {
+    - LOGGER : Logger {static}
+    + App()
+    - interpretInstruction(instruction : String, vm : VirtualMachine) {static}
+    + main(args : String[]) {static}
+  }
+  enum Instruction {
+    + ADD {static}
+    + DIVIDE {static}
+    + GET_AGILITY {static}
+    + GET_HEALTH {static}
+    + GET_WISDOM {static}
+    + LITERAL {static}
+    + PLAY_SOUND {static}
+    + SET_AGILITY {static}
+    + SET_HEALTH {static}
+    + SET_WISDOM {static}
+    + SPAWN_PARTICLES {static}
+    - value : int
+    + getInstruction(value : int) : Instruction {static}
+    + getIntValue() : int
+    + valueOf(name : String) : Instruction {static}
+    + values() : Instruction[] {static}
+  }
+  class VirtualMachine {
+    - stack : Stack<Integer>
+    - wizards : Wizard[]
+    + VirtualMachine()
+    + execute(bytecode : int[])
+    + getAgility(wizard : int) : int
+    + getHealth(wizard : int) : int
+    + getStack() : Stack<Integer>
+    + getWisdom(wizard : int) : int
+    + getWizards() : Wizard[]
+    + setAgility(wizard : int, amount : int)
+    + setHealth(wizard : int, amount : int)
+    + setWisdom(wizard : int, amount : int)
+  }
+  class Wizard {
+    - LOGGER : Logger {static}
+    - agility : int
+    - health : int
+    - numberOfPlayedSounds : int
+    - numberOfSpawnedParticles : int
+    - wisdom : int
+    + Wizard()
+    + getAgility() : int
+    + getHealth() : int
+    + getNumberOfPlayedSounds() : int
+    + getNumberOfSpawnedParticles() : int
+    + getWisdom() : int
+    + playSound()
+    + setAgility(agility : int)
+    + setHealth(health : int)
+    + setWisdom(wisdom : int)
+    + spawnParticles()
+  }
+}
+package com.iluwatar.bytecode.util {
+  class InstructionConverterUtil {
+    + InstructionConverterUtil()
+    + convertToByteCode(instructions : String) : int[] {static}
+    - isValidInstruction(instruction : String) : boolean {static}
+    - isValidInt(value : String) : boolean {static}
+  }
+}
+@enduml

bytecode/pom.xml

@@ -1,45 +1,56 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!--
+<!-- The MIT License Copyright © 2014-2019 Ilkka Seppälä Permission is hereby 
-
+	granted, free of charge, to any person obtaining a copy of this software 
-    The MIT License
+	and associated documentation files (the "Software"), to deal in the Software 
-    Copyright © 2014-2019 Ilkka Seppälä
+	without restriction, including without limitation the rights to use, copy, 
-
+	modify, merge, publish, distribute, sublicense, and/or sell copies of the 
-    Permission is hereby granted, free of charge, to any person obtaining a copy
+	Software, and to permit persons to whom the Software is furnished to do so, 
-    of this software and associated documentation files (the "Software"), to deal
+	subject to the following conditions: The above copyright notice and this 
-    in the Software without restriction, including without limitation the rights
+	permission notice shall be included in all copies or substantial portions 
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY 
-    copies of the Software, and to permit persons to whom the Software is
+	KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
-    furnished to do so, subject to the following conditions:
+	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 
-
+	NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-    The above copyright notice and this permission notice shall be included in
+	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
-    all copies or substantial portions of the Software.
+	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-
+	DEALINGS IN 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.
-
--->
 <project xmlns="http://maven.apache.org/POM/4.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <parent>
+	<parent>
-        <artifactId>java-design-patterns</artifactId>
+		<artifactId>java-design-patterns</artifactId>
-        <groupId>com.iluwatar</groupId>
+		<groupId>com.iluwatar</groupId>
-        <version>1.22.0-SNAPSHOT</version>
+		<version>1.23.0-SNAPSHOT</version>
-    </parent>
+	</parent>
-    <modelVersion>4.0.0</modelVersion>
+	<modelVersion>4.0.0</modelVersion>
 
-    <artifactId>bytecode</artifactId>
+	<artifactId>bytecode</artifactId>
-    <dependencies>
+	<dependencies>
-        <dependency>
+		<dependency>
-            <groupId>org.junit.jupiter</groupId>
+			<groupId>org.junit.jupiter</groupId>
-            <artifactId>junit-jupiter-engine</artifactId>
+			<artifactId>junit-jupiter-engine</artifactId>
-            <scope>test</scope>
+			<scope>test</scope>
-        </dependency>
+		</dependency>
-    </dependencies>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<configuration>
+							<archive>
+								<manifest>
+									<mainClass>com.iluwatar.bytecode.App</mainClass>
+								</manifest>
+							</archive>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
 
 </project>

caching/README.md

@@ -3,11 +3,10 @@ layout: pattern
 title: Caching
 folder: caching
 permalink: /patterns/caching/
-categories: Other
+categories: Behavioral
 tags:
- - Java
+  - Performance
- - Difficulty-Intermediate
+  - Cloud distributed
- - Performance
 ---
 
 ## Intent
@@ -15,6 +14,7 @@ To avoid expensive re-acquisition of resources by not releasing
 the resources immediately after their use. The resources retain their identity, are kept in some
 fast-access storage, and are re-used to avoid having to acquire them again.
 
+## Class diagram
 ![alt text](./etc/caching.png "Caching")
 
 ## Applicability
@@ -26,4 +26,4 @@ Use the Caching pattern(s) when
 
 * [Write-through, write-around, write-back: Cache explained](http://www.computerweekly.com/feature/Write-through-write-around-write-back-Cache-explained)
 * [Read-Through, Write-Through, Write-Behind, and Refresh-Ahead Caching](https://docs.oracle.com/cd/E15357_01/coh.360/e15723/cache_rtwtwbra.htm#COHDG5177)
-* [Cache-Aside](https://msdn.microsoft.com/en-us/library/dn589799.aspx)
+* [Cache-Aside pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/cache-aside)

caching/etc/caching.urm.puml

@@ -0,0 +1,119 @@
+@startuml
+package com.iluwatar.caching.constants {
+  class CachingConstants {
+    + ADD_INFO : String {static}
+    + USER_ACCOUNT : String {static}
+    + USER_ID : String {static}
+    + USER_NAME : String {static}
+    + CachingConstants()
+  }
+}
+package com.iluwatar.caching {
+  class App {
+    - LOGGER : Logger {static}
+    + App()
+    + main(args : String[]) {static}
+    + useCacheAsideStategy()
+    + useReadAndWriteThroughStrategy()
+    + useReadThroughAndWriteAroundStrategy()
+    + useReadThroughAndWriteBehindStrategy()
+  }
+  class AppManager {
+    - cachingPolicy : CachingPolicy {static}
+    - AppManager()
+    + find(userId : String) : UserAccount {static}
+    - findAside(userId : String) : UserAccount {static}
+    + initCacheCapacity(capacity : int) {static}
+    + initCachingPolicy(policy : CachingPolicy) {static}
+    + initDb(useMongoDb : boolean) {static}
+    + printCacheContent() : String {static}
+    + save(userAccount : UserAccount) {static}
+    - saveAside(userAccount : UserAccount) {static}
+  }
+  class CacheStore {
+    - LOGGER : Logger {static}
+    - cache : LruCache {static}
+    - CacheStore()
+    + clearCache() {static}
+    + flushCache() {static}
+    + get(userId : String) : UserAccount {static}
+    + initCapacity(capacity : int) {static}
+    + invalidate(userId : String) {static}
+    + print() : String {static}
+    + readThrough(userId : String) : UserAccount {static}
+    + readThroughWithWriteBackPolicy(userId : String) : UserAccount {static}
+    + set(userId : String, userAccount : UserAccount) {static}
+    + writeAround(userAccount : UserAccount) {static}
+    + writeBehind(userAccount : UserAccount) {static}
+    + writeThrough(userAccount : UserAccount) {static}
+  }
+  enum CachingPolicy {
+    + AROUND {static}
+    + ASIDE {static}
+    + BEHIND {static}
+    + THROUGH {static}
+    - policy : String
+    + getPolicy() : String
+    + valueOf(name : String) : CachingPolicy {static}
+    + values() : CachingPolicy[] {static}
+  }
+  class DbManager {
+    - db : MongoDatabase {static}
+    - mongoClient : MongoClient {static}
+    - useMongoDB : boolean {static}
+    - virtualDB : Map<String, UserAccount> {static}
+    - DbManager()
+    + connect() {static}
+    + createVirtualDb() {static}
+    + readFromDb(userId : String) : UserAccount {static}
+    + updateDb(userAccount : UserAccount) {static}
+    + upsertDb(userAccount : UserAccount) {static}
+    + writeToDb(userAccount : UserAccount) {static}
+  }
+  class LruCache {
+    - LOGGER : Logger {static}
+    ~ cache : Map<String, Node>
+    ~ capacity : int
+    ~ end : Node
+    ~ head : Node
+    + LruCache(capacity : int)
+    + clear()
+    + contains(userId : String) : boolean
+    + get(userId : String) : UserAccount
+    + getCacheDataInListForm() : List<UserAccount>
+    + getLruData() : UserAccount
+    + invalidate(userId : String)
+    + isFull() : boolean
+    + remove(node : Node)
+    + set(userId : String, userAccount : UserAccount)
+    + setCapacity(newCapacity : int)
+    + setHead(node : Node)
+  }
+  ~class Node {
+    ~ next : Node
+    ~ previous : Node
+    ~ userAccount : UserAccount
+    ~ userId : String
+    + Node(this$0 : String, userId : UserAccount)
+  }
+  class UserAccount {
+    - additionalInfo : String
+    - userId : String
+    - userName : String
+    + UserAccount(userId : String, userName : String, additionalInfo : String)
+    + getAdditionalInfo() : String
+    + getUserId() : String
+    + getUserName() : String
+    + setAdditionalInfo(additionalInfo : String)
+    + setUserId(userId : String)
+    + setUserName(userName : String)
+    + toString() : String
+  }
+}
+Node --+ LruCache
+LruCache -->  "-head" Node
+Node -->  "-previous" Node
+AppManager -->  "-cachingPolicy" CachingPolicy
+Node -->  "-userAccount" UserAccount
+CacheStore -->  "-cache" LruCache
+@enduml

caching/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.22.0-SNAPSHOT</version>
+    <version>1.23.0-SNAPSHOT</version>
   </parent>
   <artifactId>caching</artifactId>
   <dependencies>
@@ -41,7 +41,7 @@
     <dependency>
       <groupId>org.mongodb</groupId>
       <artifactId>mongodb-driver</artifactId>
-      <version>3.0.4</version>
+      <version>3.12.1</version>
     </dependency>
     <dependency>
       <groupId>org.mongodb</groupId>
@@ -69,6 +69,21 @@
           <skipTests>false</skipTests>
         </configuration>
       </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.caching.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
     </plugins>
   </build>
 </project>

callback/README.md

@@ -3,19 +3,72 @@ layout: pattern
 title: Callback
 folder: callback
 permalink: /patterns/callback/
-categories: Other
+categories: Idiom
 tags:
- - Java
+ - Reactive
- - Difficulty-Beginner
- - Functional
- - Idiom
 ---
 
 ## Intent
-Callback is a piece of executable code that is passed as an
+Callback is a piece of executable code that is passed as an argument to other code, which is expected to call back 
-argument to other code, which is expected to call back (execute) the argument
+(execute) the argument at some convenient time.
-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.     
+
+In plain words
+
+> Callback is a method passed to the executor which will be called at defined moment. 
+
+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.
+
+**Programmatic Example**
+
+Callback is a simple interface with single method.
+
+```java
+public interface Callback {
+
+  void call();
+}
+```
+
+Next we define a task that will execute the callback after the task execution has finished.
+
+```java
+public abstract class Task {
+
+  final void executeWith(Callback callback) {
+    execute();
+    Optional.ofNullable(callback).ifPresent(Callback::call);
+  }
+
+  public abstract void execute();
+}
+
+public final class SimpleTask extends Task {
+
+  private static final Logger LOGGER = getLogger(SimpleTask.class);
+
+  @Override
+  public void execute() {
+    LOGGER.info("Perform some important activity and after call the callback method.");
+  }
+}
+```
+
+Finally here's how we execute a task and receive a callback when it's finished.
+
+```java
+    var task = new SimpleTask();
+    task.executeWith(() -> LOGGER.info("I'm done now."));
+```
+
+## Class diagram
 ![alt text](./etc/callback.png "Callback")
 
 ## Applicability

callback/etc/callback.urm.puml

@@ -0,0 +1,28 @@
+@startuml
+package com.iluwatar.callback {
+  class App {
+    - LOGGER : Logger {static}
+    - App()
+    + main(args : String[]) {static}
+  }
+  interface Callback {
+    + call() {abstract}
+  }
+  class LambdasApp {
+    - LOGGER : Logger {static}
+    - LambdasApp()
+    + main(args : String[]) {static}
+  }
+  class SimpleTask {
+    - LOGGER : Logger {static}
+    + SimpleTask()
+    + execute()
+  }
+  abstract class Task {
+    + Task()
+    + execute() {abstract}
+    ~ executeWith(callback : Callback)
+  }
+}
+SimpleTask --|> Task 
+@enduml

callback/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.22.0-SNAPSHOT</version>
+    <version>1.23.0-SNAPSHOT</version>
   </parent>
   <artifactId>callback</artifactId>
   <dependencies>
@@ -39,4 +39,23 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.callback.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
 </project>

callback/src/main/java/com/iluwatar/callback/Task.java

@@ -33,7 +33,7 @@ public abstract class Task {
   /**
    * Execute with callback.
    */
-  final void executeWith(final Callback callback) {
+  final void executeWith(Callback callback) {
     execute();
     Optional.ofNullable(callback).ifPresent(Callback::call);
   }

callback/src/main/java/com/iluwatar/callback/module-info.java

@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */
+
+module com.iluwatar.callback {
+	requires org.slf4j;
+}

chain/README.md

@@ -5,9 +5,7 @@ folder: chain
 permalink: /patterns/chain/
 categories: Behavioral
 tags:
- - Java
+ - Gang of Four
- - Gang Of Four
- - Difficulty-Intermediate
 ---
 
 ## Intent
@@ -141,6 +139,9 @@ king.makeRequest(new Request(RequestType.TORTURE_PRISONER, "torture prisoner"));
 king.makeRequest(new Request(RequestType.COLLECT_TAX, "collect tax")); // Orc soldier handling request "collect tax"
 ```
 
+## Class diagram
+![alt text](./etc/chain.urm.png "Chain of Responsibility class diagram")
+
 ## Applicability
 Use Chain of Responsibility when
 
@@ -156,4 +157,5 @@ Use Chain of Responsibility when
 
 ## Credits
 
-* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://www.amazon.com/gp/product/0201633612/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0201633612&linkCode=as2&tag=javadesignpat-20&linkId=675d49790ce11db99d90bde47f1aeb59)
+* [Head First Design Patterns: A Brain-Friendly Guide](https://www.amazon.com/gp/product/0596007124/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596007124&linkCode=as2&tag=javadesignpat-20&linkId=6b8b6eea86021af6c8e3cd3fc382cb5b)

chain/etc/chain.urm.puml

@@ -0,0 +1,61 @@
+@startuml
+package com.iluwatar.chain {
+  class App {
+    + App()
+    + main(args : String[]) {static}
+  }
+  class OrcCommander {
+    + OrcCommander(handler : RequestHandler)
+    + handleRequest(req : Request)
+    + toString() : String
+  }
+  class OrcKing {
+    - chain : RequestHandler
+    + OrcKing()
+    - buildChain()
+    + makeRequest(req : Request)
+  }
+  class OrcOfficer {
+    + OrcOfficer(handler : RequestHandler)
+    + handleRequest(req : Request)
+    + toString() : String
+  }
+  class OrcSoldier {
+    + OrcSoldier(handler : RequestHandler)
+    + handleRequest(req : Request)
+    + toString() : String
+  }
+  class Request {
+    - handled : boolean
+    - requestDescription : String
+    - requestType : RequestType
+    + Request(requestType : RequestType, requestDescription : String)
+    + getRequestDescription() : String
+    + getRequestType() : RequestType
+    + isHandled() : boolean
+    + markHandled()
+    + toString() : String
+  }
+  abstract class RequestHandler {
+    - LOGGER : Logger {static}
+    - next : RequestHandler
+    + RequestHandler(next : RequestHandler)
+    + handleRequest(req : Request)
+    # printHandling(req : Request)
+    + toString() : String {abstract}
+  }
+  enum RequestType {
+    + COLLECT_TAX {static}
+    + DEFEND_CASTLE {static}
+    + TORTURE_PRISONER {static}
+    + valueOf(name : String) : RequestType {static}
+    + values() : RequestType[] {static}
+  }
+}
+OrcKing -->  "-chain" RequestHandler
+RequestHandler -->  "-next" RequestHandler
+Request -->  "-requestType" RequestType
+OrcCommander --|> RequestHandler 
+OrcOfficer --|> RequestHandler 
+OrcSoldier --|> RequestHandler 
+@enduml

chain/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.22.0-SNAPSHOT</version>
+    <version>1.23.0-SNAPSHOT</version>
   </parent>
   <artifactId>chain</artifactId>
   <dependencies>
@@ -39,4 +39,23 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.chain.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
 </project>

chain/src/main/java/com/iluwatar/chain/module-info.java

@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */
+
+module com.iluwatar.chain {
+	requires org.slf4j;
+}

circuit-breaker/README.md

@@ -3,11 +3,11 @@ layout: pattern
 title: Circuit Breaker
 folder: circuit-breaker
 permalink: /patterns/circuit-breaker/
-categories: Other
+categories: Behavioral
 tags:
- - Java
+  - Performance
- - Performance
+  - Decoupling
- - Difficulty-Intermediate
+  - Cloud distributed
 ---
 
 ## Intent
@@ -165,6 +165,8 @@ How does the above pattern prevent failures? Let's understand via this finite st
 - 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
@@ -177,6 +179,7 @@ Use the Circuit Breaker pattern when
 - [Retry Pattern](https://github.com/iluwatar/java-design-patterns/tree/master/retry)
 
 ## Real world examples
+
 * [Spring Circuit Breaker module](https://spring.io/guides/gs/circuit-breaker)
 * [Netflix Hystrix API](https://github.com/Netflix/Hystrix)
 
@@ -185,4 +188,4 @@ Use the Circuit Breaker pattern when
 * [Understanding Circuit Breaker Pattern](https://itnext.io/understand-circuitbreaker-design-pattern-with-simple-practical-example-92a752615b42)
 * [Martin Fowler on Circuit Breaker](https://martinfowler.com/bliki/CircuitBreaker.html)
 * [Fault tolerance in a high volume, distributed system](https://medium.com/netflix-techblog/fault-tolerance-in-a-high-volume-distributed-system-91ab4faae74a)
-* [Microsoft docs](https://docs.microsoft.com/en-us/azure/architecture/patterns/circuit-breaker)
+* [Circuit Breaker pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/circuit-breaker)

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

@@ -0,0 +1,44 @@
+@startuml
+package com.iluwatar.circuitbreaker {
+  class App {
+    - LOGGER : Logger {static}
+    + App()
+    + main(args : String[]) {static}
+  }
+  class CircuitBreaker {
+    ~ failureCount : int
+    - failureThreshold : int
+    - futureTime : long
+    ~ lastFailureTime : long
+    - retryTimePeriod : long
+    - state : State
+    - timeout : long
+    ~ CircuitBreaker(timeout : long, failureThreshold : int, retryTimePeriod : long)
+    + call(serviceToCall : String, serverStartTime : long) : String
+    + getState() : String
+    - recordFailure()
+    - reset()
+    # setState()
+    + setStateForBypass(state : State)
+  }
+  class DelayedService {
+    - delay : int
+    + DelayedService()
+    + DelayedService(delay : int)
+    + response(serverStartTime : long) : String
+  }
+  class MonitoringService {
+    + MonitoringService()
+    + localResourceResponse() : String
+    + remoteResourceResponse(circuitBreaker : CircuitBreaker, serverStartTime : long) : String
+  }
+  enum State {
+    + CLOSED {static}
+    + HALF_OPEN {static}
+    + OPEN {static}
+    + valueOf(name : String) : State {static}
+    + values() : State[] {static}
+  }
+}
+CircuitBreaker -->  "-state" State
+@enduml

circuit-breaker/pom.xml

@@ -27,7 +27,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.22.0-SNAPSHOT</version>
+        <version>1.23.0-SNAPSHOT</version>
     </parent>
     <artifactId>circuit-breaker</artifactId>
     <dependencies>
@@ -37,4 +37,23 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
+    <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.circuitbreaker.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
 </project>

collection-pipeline/README.md

@@ -3,17 +3,16 @@ layout: pattern
 title: Collection Pipeline
 folder: collection-pipeline
 permalink: /patterns/collection-pipeline/
-categories: Other
+categories: Functional
 tags:
- - Java
+ - Reactive
- - Difficulty-Beginner
- - Functional
 ---
 
 ## Intent
 Collection Pipeline introduces Function Composition and Collection Pipeline, two functional-style patterns that you can combine to iterate collections in your code. 
 In functional programming, it's common to sequence complex operations through a series of smaller modular functions or operations. The series is called a composition of functions, or a function composition. When a collection of data flows through a function composition, it becomes a collection pipeline. Function Composition and Collection Pipeline are two design patterns frequently used in functional-style programming.
 
+## Class diagram
 ![alt text](./etc/collection-pipeline.png "Collection Pipeline")
 
 ## Applicability
@@ -27,4 +26,4 @@ Use the Collection Pipeline pattern when
 
 * [Function composition and the Collection Pipeline pattern](https://www.ibm.com/developerworks/library/j-java8idioms2/index.html)
 * [Martin Fowler](https://martinfowler.com/articles/collection-pipeline/)
-* [Java8 Streams](https://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html)
+* [Java8 Streams](https://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html)

collection-pipeline/etc/collection-pipeline.urm.puml

@@ -0,0 +1,52 @@
+@startuml
+package com.iluwatar.collectionpipeline {
+  class App {
+    - LOGGER : Logger {static}
+    + App()
+    + main(args : String[]) {static}
+  }
+  class Car {
+    - category : Category
+    - make : String
+    - model : String
+    - year : int
+    + Car(make : String, model : String, yearOfMake : int, category : Category)
+    + equals(obj : Object) : boolean
+    + getCategory() : Category
+    + getMake() : String
+    + getModel() : String
+    + getYear() : int
+    + hashCode() : int
+  }
+  class CarFactory {
+    - CarFactory()
+    + createCars() : List<Car> {static}
+  }
+  enum Category {
+    + CONVERTIBLE {static}
+    + JEEP {static}
+    + SEDAN {static}
+    + valueOf(name : String) : Category {static}
+    + values() : Category[] {static}
+  }
+  class FunctionalProgramming {
+    - FunctionalProgramming()
+    + getGroupingOfCarsByCategory(cars : List<Car>) : Map<Category, List<Car>> {static}
+    + getModelsAfter2000(cars : List<Car>) : List<String> {static}
+    + getSedanCarsOwnedSortedByDate(persons : List<Person>) : List<Car> {static}
+  }
+  class ImperativeProgramming {
+    - ImperativeProgramming()
+    + getGroupingOfCarsByCategory(cars : List<Car>) : Map<Category, List<Car>> {static}
+    + getModelsAfter2000(cars : List<Car>) : List<String> {static}
+    + getSedanCarsOwnedSortedByDate(persons : List<Person>) : List<Car> {static}
+  }
+  class Person {
+    - cars : List<Car>
+    + Person(cars : List<Car>)
+    + getCars() : List<Car>
+  }
+}
+Person -->  "-cars" Car
+Car -->  "-category" Category
+@enduml

collection-pipeline/pom.xml

@@ -27,7 +27,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.22.0-SNAPSHOT</version>
+    <version>1.23.0-SNAPSHOT</version>
   </parent>
   <artifactId>collection-pipeline</artifactId>
   <dependencies>
@@ -37,4 +37,23 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-assembly-plugin</artifactId>
+        <executions>
+          <execution>
+            <configuration>
+              <archive>
+                <manifest>
+                  <mainClass>com.iluwatar.collectionpipeline.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
 </project>

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/ImperativeProgramming.java

@@ -23,12 +23,12 @@
 
 package com.iluwatar.collectionpipeline;
 
-import java.util.Collection;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
 
 /**
  * Imperative-style programming to iterate over the list and get the names of cars made later than
@@ -57,11 +57,27 @@ public class ImperativeProgramming {
    * @return {@link List} of {@link String} of car models built after year 2000
    */
   public static List<String> getModelsAfter2000(List<Car> cars) {
-    return cars.stream()
+    List<Car> carsSortedByYear = new ArrayList<>();
-        .filter(car -> car.getYear() > 2000)
+
-        .sorted(Comparator.comparingInt(Car::getYear))
+    for (Car car : cars) {
-        .map(Car::getModel)
+      if (car.getYear() > 2000) {
-        .collect(Collectors.toList());
+        carsSortedByYear.add(car);
+      }
+    }
+
+    Collections.sort(carsSortedByYear, new Comparator<Car>() {
+      @Override
+      public int compare(Car car1, Car car2) {
+        return car1.getYear() - car2.getYear();
+      }
+    });
+
+    List<String> models = new ArrayList<>();
+    for (Car car : carsSortedByYear) {
+      models.add(car.getModel());
+    }
+
+    return models;
   }
 
   /**
@@ -71,7 +87,17 @@ public class ImperativeProgramming {
    * @return {@link Map} with category as key and cars belonging to that category as value
    */
   public static Map<Category, List<Car>> getGroupingOfCarsByCategory(List<Car> cars) {
-    return cars.stream().collect(Collectors.groupingBy(Car::getCategory));
+    Map<Category, List<Car>> groupingByCategory = new HashMap<>();
+    for (Car car : cars) {
+      if (groupingByCategory.containsKey(car.getCategory())) {
+        groupingByCategory.get(car.getCategory()).add(car);
+      } else {
+        List<Car> categoryCars = new ArrayList<>();
+        categoryCars.add(car);
+        groupingByCategory.put(car.getCategory(), categoryCars);
+      }
+    }
+    return groupingByCategory;
   }
 
   /**
@@ -82,11 +108,25 @@ public class ImperativeProgramming {
    * @return {@link List} of {@link Car} to belonging to the group
    */
   public static List<Car> getSedanCarsOwnedSortedByDate(List<Person> persons) {
-    return persons.stream()
+    List<Car> cars = new ArrayList<>();
-        .map(Person::getCars)
+    for (Person person : persons) {
-        .flatMap(Collection::stream)
+      cars.addAll(person.getCars());
-        .filter(car -> car.getCategory() == Category.SEDAN)
+    }
-        .sorted(Comparator.comparingInt(Car::getYear))
+
-        .collect(Collectors.toList());
+    List<Car> sedanCars = new ArrayList<>();
+    for (Car car : cars) {
+      if (Category.SEDAN.equals(car.getCategory())) {
+        sedanCars.add(car);
+      }
+    }
+
+    sedanCars.sort(new Comparator<Car>() {
+      @Override
+      public int compare(Car o1, Car o2) {
+        return o1.getYear() - o2.getYear();
+      }
+    });
+
+    return sedanCars;
   }
 }

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/module-info.java

@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */
+
+module com.iluwatar.collectionpipeline {
+	requires org.slf4j;
+}

combinator/README.md

@@ -0,0 +1,36 @@
+---
+layout: pattern
+title: Combinator
+folder: combinator
+permalink: /patterns/combinator/
+categories: Idiom
+tags:
+ - Reactive
+---
+
+## Also known as
+Composition pattern
+
+## Intent
+The functional pattern representing a style of organizing libraries centered around the idea of combining functions.  
+Putting it simply, there is some type T, some functions for constructing "primitive" values of type T, 
+and some "combinators" which can combine values of type T in various ways to build up more complex values of type T.
+
+## Class diagram
+![alt text](./etc/combinator.urm.png "Combinator class diagram")
+
+## Applicability
+Use the combinator pattern when:
+
+- You are able to create a more complex value from more plain values but having the same type(a combination of them)
+
+## Real world examples
+
+- java.util.function.Function#compose
+- java.util.function.Function#andThen
+
+## Credits
+
+- [Example for java](https://gtrefs.github.io/code/combinator-pattern/)
+- [Combinator pattern](https://wiki.haskell.org/Combinator_pattern)
+- [Combinatory logic](https://wiki.haskell.org/Combinatory_logic)

combinator/etc/combinator.urm.puml

@@ -0,0 +1,26 @@
+@startuml
+package com.iluwatar.combinator {
+  class CombinatorApp {
+    - LOGGER : Logger {static}
+    + CombinatorApp()
+    + main(args : String[]) {static}
+    - text() : String {static}
+  }
+  interface Finder {
+    + and(andFinder : Finder) : Finder
+    + contains(word : String) : Finder {static}
+    + find(String) : List<String> {abstract}
+    + not(notFinder : Finder) : Finder
+    + or(orFinder : Finder) : Finder
+  }
+  class Finders {
+    - Finders()
+    + advancedFinder(query : String, orQuery : String, notQuery : String) : Finder {static}
+    + expandedFinder(queries : String[]) : Finder {static}
+    + filteredFinder(query : String, excludeQueries : String[]) : Finder {static}
+    - identMult() : Finder {static}
+    - identSum() : Finder {static}
+    + specializedFinder(queries : String[]) : Finder {static}
+  }
+}
+@enduml

combinator/pom.xml

@@ -0,0 +1,44 @@
+<?xml version="1.0"?>
+<!--
+
+    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.
+
+-->
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.23.0-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>combinator</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+</project>

combinator/src/main/java/com/iluwatar/combinator/CombinatorApp.java

@@ -0,0 +1,92 @@
+/*
+ * 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.combinator;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+ * The functional pattern representing a style of organizing libraries
+ * centered around the idea of combining functions.
+ * Putting it simply, there is some type T, some functions
+ * for constructing "primitive" values of type T,
+ * and some "combinators" which can combine values of type T
+ * in various ways to build up more complex values of type T.
+ * The class {@link Finder} defines a simple function {@link Finder#find(String)}
+ * and connected functions
+ * {@link Finder#or(Finder)},
+ * {@link Finder#not(Finder)},
+ * {@link Finder#and(Finder)}
+ * Using them the became possible to get more complex functions {@link Finders}
+ */
+public class CombinatorApp {
+
+  /**
+   * Logger.
+   */
+  private static final Logger LOGGER = LoggerFactory.getLogger(CombinatorApp.class);
+
+  /**
+   * main.
+   * @param args args
+   */
+  public static void main(String[] args) {
+    var queriesOr = new String[]{"many", "Annabel"};
+    var finder = Finders.expandedFinder(queriesOr);
+    var res = finder.find(text());
+    LOGGER.info("the result of expanded(or) query[{}] is {}", queriesOr, res);
+
+    var queriesAnd = new String[]{"Annabel", "my"};
+    finder = Finders.specializedFinder(queriesAnd);
+    res = finder.find(text());
+    LOGGER.info("the result of specialized(and) query[{}] is {}", queriesAnd, res);
+
+    finder = Finders.advancedFinder("it was","kingdom","sea");
+    res = finder.find(text());
+    LOGGER.info("the result of advanced query is {}", res);
+
+    res = Finders.filteredFinder(" was ", "many", "child").find(text());
+    LOGGER.info("the result of filtered query is {}", res);
+
+
+  }
+
+  private static String text() {
+    return
+        "It was many and many a year ago,\n"
+            + "In a kingdom by the sea,\n"
+            + "That a maiden there lived whom you may know\n"
+            + "By the name of ANNABEL LEE;\n"
+            + "And this maiden she lived with no other thought\n"
+            + "Than to love and be loved by me.\n"
+            + "I was a child and she was a child,\n"
+            + "In this kingdom by the sea;\n"
+            + "But we loved with a love that was more than love-\n"
+            + "I and my Annabel Lee;\n"
+            + "With a love that the winged seraphs of heaven\n"
+            + "Coveted her and me.";
+  }
+
+}

combinator/src/main/java/com/iluwatar/combinator/Finder.java

@@ -0,0 +1,93 @@
+/*
+ * 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.combinator;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+/**
+ * Functional interface to find lines in text.
+ */
+public interface Finder {
+
+  /**
+   * The function to find lines in text.
+   * @param text full tet
+   * @return result of searching
+   */
+  List<String> find(String text);
+
+  /**
+   * Simple implementation of function {@link #find(String)}.
+   * @param word for searching
+   * @return this
+   */
+  static Finder contains(String word) {
+    return txt -> Stream.of(txt.split("\n"))
+        .filter(line -> line.toLowerCase().contains(word.toLowerCase()))
+        .collect(Collectors.toList());
+  }
+
+  /**
+   * combinator not.
+   * @param notFinder finder to combine
+   * @return new finder including previous finders
+   */
+  default Finder not(Finder notFinder) {
+    return txt -> {
+      List<String> res = this.find(txt);
+      res.removeAll(notFinder.find(txt));
+      return res;
+    };
+  }
+
+  /**
+   * combinator or.
+   * @param orFinder finder to combine
+   * @return new finder including previous finders
+   */
+  default Finder or(Finder orFinder) {
+    return txt -> {
+      List<String> res = this.find(txt);
+      res.addAll(orFinder.find(txt));
+      return res;
+    };
+  }
+
+  /**
+   * combinator or.
+   * @param andFinder finder to combine
+   * @return new finder including previous finders
+   */
+  default Finder and(Finder andFinder) {
+    return
+        txt -> this
+            .find(txt)
+            .stream()
+            .flatMap(line -> andFinder.find(line).stream())
+            .collect(Collectors.toList());
+  }
+
+}