docs: update .all-contributorsrc [skip ci]

fix word typo

.all-contributorsrc

@@ -1045,7 +1045,8 @@
       "avatar_url": "https://avatars1.githubusercontent.com/u/6307904?v=4",
       "profile": "https://github.com/charlesfinley",
       "contributions": [
-        "code"
+        "code",
+        "review"
       ]
     },
     {
@@ -1065,6 +1066,51 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "raja-peeyush-kumar-singh",
+      "name": "Peeyush",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/5496024?v=4",
+      "profile": "https://github.com/raja-peeyush-kumar-singh",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "ravening",
+      "name": "Rakesh",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/10645273?v=4",
+      "profile": "https://github.com/ravening",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "vINCENT8888801",
+      "name": "Wei Seng",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/8037883?v=4",
+      "profile": "https://github.com/vINCENT8888801",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "ashishtrivedi16",
+      "name": "Ashish Trivedi",
+      "avatar_url": "https://avatars3.githubusercontent.com/u/23194128?v=4",
+      "profile": "https://www.linkedin.com/in/ashish-trivedi-218379135/",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "RayYH",
+      "name": "洪月阳",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/41055099?v=4",
+      "profile": "https://rayyounghong.com",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 4,

README.md

@@ -9,7 +9,7 @@
 [![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-117-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-122-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 # Introduction
@@ -239,11 +239,18 @@ This project is licensed under the terms of the MIT license.
   <tr>
     <td align="center"><a href="https://webpro.nl"><img src="https://avatars1.githubusercontent.com/u/456426?v=4" width="100px;" alt=""/><br /><sub><b>Lars Kappert</b></sub></a><br /><a href="#content-webpro" title="Content">🖋</a></td>
     <td align="center"><a href="https://xiaod.info"><img src="https://avatars2.githubusercontent.com/u/21277644?v=4" width="100px;" alt=""/><br /><sub><b>Mike Liu</b></sub></a><br /><a href="#translation-xiaod-dev" title="Translation">🌍</a></td>
-    <td align="center"><a href="https://github.com/charlesfinley"><img src="https://avatars1.githubusercontent.com/u/6307904?v=4" width="100px;" alt=""/><br /><sub><b>Matt Dolan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=charlesfinley" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/charlesfinley"><img src="https://avatars1.githubusercontent.com/u/6307904?v=4" width="100px;" alt=""/><br /><sub><b>Matt Dolan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=charlesfinley" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Acharlesfinley" title="Reviewed Pull Requests">👀</a></td>
     <td align="center"><a href="https://github.com/MananS77"><img src="https://avatars3.githubusercontent.com/u/21033516?v=4" width="100px;" alt=""/><br /><sub><b>Manan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AMananS77" title="Reviewed Pull Requests">👀</a></td>
   </tr>
   <tr>
     <td align="center"><a href="https://github.com/nishant"><img src="https://avatars2.githubusercontent.com/u/15331971?v=4" width="100px;" alt=""/><br /><sub><b>Nishant Arora</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nishant" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/raja-peeyush-kumar-singh"><img src="https://avatars0.githubusercontent.com/u/5496024?v=4" width="100px;" alt=""/><br /><sub><b>Peeyush</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=raja-peeyush-kumar-singh" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ravening"><img src="https://avatars1.githubusercontent.com/u/10645273?v=4" width="100px;" alt=""/><br /><sub><b>Rakesh</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ravening" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/vINCENT8888801"><img src="https://avatars0.githubusercontent.com/u/8037883?v=4" width="100px;" alt=""/><br /><sub><b>Wei Seng</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vINCENT8888801" title="Code">💻</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://www.linkedin.com/in/ashish-trivedi-218379135/"><img src="https://avatars3.githubusercontent.com/u/23194128?v=4" width="100px;" alt=""/><br /><sub><b>Ashish Trivedi</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ashishtrivedi16" title="Code">💻</a></td>
+    <td align="center"><a href="https://rayyounghong.com"><img src="https://avatars1.githubusercontent.com/u/41055099?v=4" width="100px;" alt=""/><br /><sub><b>洪月阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=RayYH" title="Code">💻</a></td>
   </tr>
 </table>
 

abstract-document/src/main/java/com/iluwatar/abstractdocument/App.java

@@ -43,9 +43,11 @@ public class App {
   private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
 
   /**
-   * Executes the App.
+   * Program entry point.
+   *
+   * @param args command line args
    */
-  public App() {
+  public static void main(String[] args) {
     LOGGER.info("Constructing parts and car");
 
     var wheelProperties = Map.of(
@@ -75,14 +77,4 @@ public class App {
         p.getPrice().orElse(null))
     );
   }
-
-  /**
-   * Program entry point.
-   *
-   * @param args command line args
-   */
-  public static void main(String[] args) {
-    new App();
-  }
-
 }

abstract-document/src/test/java/com/iluwatar/abstractdocument/AbstractDocumentTest.java

@@ -40,7 +40,7 @@ public class AbstractDocumentTest {
   private static final String KEY = "key";
   private static final String VALUE = "value";
 
-  private class DocumentImplementation extends AbstractDocument {
+  private static class DocumentImplementation extends AbstractDocument {
 
     DocumentImplementation(Map<String, Object> properties) {
       super(properties);

abstract-factory/README.md

@@ -9,16 +9,19 @@ tags:
 ---
 
 ## Also known as
+
 Kit
 
 ## Intent
+
 Provide an interface for creating families of related or dependent
 objects without specifying their concrete classes.
 
 ## Explanation
+
 Real world example
 
-> To create a kingdom we need objects with common theme. Elven kingdom needs an Elven king, Elven castle and Elven army whereas Orcish kingdom needs an Orcish king, Orcish castle and Orcish army. There is a dependency between the objects in the kingdom.
+> To create a kingdom we need objects with a common theme. Elven kingdom needs an Elven king, Elven castle and Elven army whereas Orcish kingdom needs an Orcish king, Orcish castle and Orcish army. There is a dependency between the objects in the kingdom.
 
 In plain words
 
@@ -30,15 +33,18 @@ Wikipedia says
 
 **Programmatic Example**
 
-Translating the kingdom example above. First of all we have some interfaces and implementation for the objects in the kingdom
+Translating the kingdom example above. First of all we have some interfaces and implementation for the objects in the 
+kingdom.
 
 ```java
 public interface Castle {
   String getDescription();
 }
+
 public interface King {
   String getDescription();
 }
+
 public interface Army {
   String getDescription();
 }
@@ -66,7 +72,7 @@ public class ElfArmy implements Army {
   }
 }
 
-// Orcish implementations similarly...
+// Orcish implementations similarly -> ...
 
 ```
 
@@ -112,9 +118,17 @@ var castle = factory.createCastle();
 var king = factory.createKing();
 var army = factory.createArmy();
 
-castle.getDescription();  // Output: This is the Elven castle!
-king.getDescription(); // Output: This is the Elven king!
-army.getDescription(); // Output: This is the Elven Army!
+castle.getDescription();
+king.getDescription();
+army.getDescription();
+```
+
+Program output:
+
+```java
+This is the Elven castle!
+This is the Elven king!
+This is the Elven Army!
 ```
 
 Now, we can design a factory for our different kingdom factories. In this example, we created FactoryMaker, responsible for returning an instance of either ElfKingdomFactory or OrcKingdomFactory.  
@@ -156,46 +170,52 @@ 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
 
-* a system should be independent of how its products are created, composed and represented
-* a system should be configured with one of multiple families of products
-* a family of related product objects is designed to be used together, and you need to enforce this constraint
-* you want to provide a class library of products, and you want to reveal just their interfaces, not their implementations
-* the lifetime of the dependency is conceptually shorter than the lifetime of the consumer.
-*	you need a run-time value to construct a particular dependency
-*	you want to decide which product to call from a family at runtime.
-*	you need to supply one or more parameters only known at run-time before you can resolve a dependency.
-* when you need consistency among products
-* you don’t want to change existing code when adding new products or families of products to the program.
+* The system should be independent of how its products are created, composed and represented
+* The system should be configured with one of multiple families of products
+* The family of related product objects is designed to be used together, and you need to enforce this constraint
+* You want to provide a class library of products, and you want to reveal just their interfaces, not their implementations
+* The lifetime of the dependency is conceptually shorter than the lifetime of the consumer.
+* You need a run-time value to construct a particular dependency
+* You want to decide which product to call from a family at runtime.
+* You need to supply one or more parameters only known at run-time before you can resolve a dependency.
+* When you need consistency among products
+* You don’t want to change existing code when adding new products or families of products to the program.
 
-## Use Cases:	
+Example use cases	
 
-*	Selecting to call the appropriate implementation of FileSystemAcmeService or DatabaseAcmeService or NetworkAcmeService at runtime.
-*	Unit test case writing becomes much easier
+* Selecting to call to the appropriate implementation of FileSystemAcmeService or DatabaseAcmeService or NetworkAcmeService at runtime.
+* Unit test case writing becomes much easier
 * UI tools for different OS
 
 ## Consequences:
 
-*	Dependency injection in java hides the service class dependencies that can lead to runtime errors that would have been caught at compile time.
+* Dependency injection in java hides the service class dependencies that can lead to runtime errors that would have been caught at compile time.
 * While the pattern is great when creating predefined objects, adding the new ones might be challenging.
-* The code may become more complicated than it should be, since a lot of new interfaces and classes are introduced along with the pattern.
-
+* The code becomes more complicated than it should be, since a lot of new interfaces and classes are introduced along with the pattern.
 
 ## Tutorial
+
 * [Abstract Factory Pattern Tutorial](https://www.journaldev.com/1418/abstract-factory-design-pattern-in-java) 
 
-
-## Real world examples
+## Known uses
 
 * [javax.xml.parsers.DocumentBuilderFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/parsers/DocumentBuilderFactory.html)
 * [javax.xml.transform.TransformerFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/transform/TransformerFactory.html#newInstance--)
 * [javax.xml.xpath.XPathFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/xpath/XPathFactory.html#newInstance--)
 
+## Related patterns
+
+[Factory Method](https://java-design-patterns.com/patterns/factory-method/)
+[Factory Kit](https://java-design-patterns.com/patterns/factory-kit/)
+
 ## Credits
 
 * [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)

acyclic-visitor/README.md

@@ -9,12 +9,126 @@ tags:
 ---
 
 ## 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.
+
+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.
+
+## Explanation
+
+Real world example
+
+> We have a hierarchy of modem classes. The modems in this hierarchy need to be visited by an external algorithm based 
+> on filtering criteria (is it Unix or DOS compatible modem). 
+
+In plain words
+
+> Acyclic Visitor allows functions to be added to existing class hierarchies without modifying the hierarchies.
+
+[WikiWikiWeb](https://wiki.c2.com/?AcyclicVisitor) says
+
+> The Acyclic Visitor pattern allows new functions to be added to existing class hierarchies without affecting those 
+> hierarchies, and without creating the dependency cycles that are inherent to the GangOfFour VisitorPattern.
+
+**Programmatic Example**
+
+Here's the `Modem` hierarchy.
+
+```java
+public abstract class Modem {
+  public abstract void accept(ModemVisitor modemVisitor);
+}
+
+public class Zoom extends Modem {
+  ...
+  @Override
+  public void accept(ModemVisitor modemVisitor) {
+    if (modemVisitor instanceof ZoomVisitor) {
+      ((ZoomVisitor) modemVisitor).visit(this);
+    } else {
+      LOGGER.info("Only ZoomVisitor is allowed to visit Zoom modem");
+    }
+  }
+}
+
+public class Hayes extends Modem {
+  ...
+  @Override
+  public void accept(ModemVisitor modemVisitor) {
+    if (modemVisitor instanceof HayesVisitor) {
+      ((HayesVisitor) modemVisitor).visit(this);
+    } else {
+      LOGGER.info("Only HayesVisitor is allowed to visit Hayes modem");
+    }
+  }
+}
+```
+
+Next we introduce the `ModemVisitor` hierarchy.
+
+```java
+public interface ModemVisitor {
+}
+
+public interface HayesVisitor extends ModemVisitor {
+  void visit(Hayes hayes);
+}
+
+public interface ZoomVisitor extends ModemVisitor {
+  void visit(Zoom zoom);
+}
+
+public interface AllModemVisitor extends ZoomVisitor, HayesVisitor {
+}
+
+public class ConfigureForDosVisitor implements AllModemVisitor {
+  ...
+  @Override
+  public void visit(Hayes hayes) {
+    LOGGER.info(hayes + " used with Dos configurator.");
+  }
+  @Override
+  public void visit(Zoom zoom) {
+    LOGGER.info(zoom + " used with Dos configurator.");
+  }
+}
+
+public class ConfigureForUnixVisitor implements ZoomVisitor {
+  ...
+  @Override
+  public void visit(Zoom zoom) {
+    LOGGER.info(zoom + " used with Unix configurator.");
+  }
+}
+```
+
+Finally, here are the visitors in action.
+
+```java
+    var conUnix = new ConfigureForUnixVisitor();
+    var conDos = new ConfigureForDosVisitor();
+    var zoom = new Zoom();
+    var hayes = new Hayes();
+    hayes.accept(conDos);
+    zoom.accept(conDos);
+    hayes.accept(conUnix);
+    zoom.accept(conUnix);   
+```
+
+Program output:
+
+```
+    // Hayes modem used with Dos configurator.
+    // Zoom modem used with Dos configurator.
+    // Only HayesVisitor is allowed to visit Hayes modem
+    // Zoom modem used with Unix configurator.
+```
 
 ## 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.
@@ -24,6 +138,7 @@ This pattern can be used:
 * When the recompilation, relinking, retesting or redistribution of the derivatives of Element is very expensive.
 
 ## Consequences
+
 The good:
 
 * No dependency cycles between class hierarchies.
@@ -32,11 +147,14 @@ The good:
 
 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.
+* Violates [Liskov's Substitution Principle](https://java-design-patterns.com/principles/#liskov-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.
 
 ## Related patterns
-* [Visitor Pattern](../visitor/)
+
+* [Visitor Pattern](https://java-design-patterns.com/patterns/visitor/)
 
 ## Credits
-* [Acyclic Visitor](http://condor.depaul.edu/dmumaugh/OOT/Design-Principles/acv.pdf)
+
+* [Acyclic Visitor by Robert C. Martin](http://condor.depaul.edu/dmumaugh/OOT/Design-Principles/acv.pdf)
+* [Acyclic Visitor in WikiWikiWeb](https://wiki.c2.com/?AcyclicVisitor)

acyclic-visitor/etc/Acyclic Visitor.ucls

@@ -1,115 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<class-diagram version="1.2.2" icons="true" always-add-relationships="false" generalizations="true" realizations="true" 
-  associations="true" dependencies="false" nesting-relationships="true" router="FAN">  
-  <interface id="1" language="java" name="com.iluwatar.acyclicvisitor.ModemVisitor" project="acyclic-visitor" 
-    file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ModemVisitor.java" binary="false" 
-    corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="860" y="67"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </interface>  
-  <class id="2" language="java" name="com.iluwatar.acyclicvisitor.Modem" project="acyclic-visitor" 
-    file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Modem.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="327" y="77"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <class id="3" language="java" name="com.iluwatar.acyclicvisitor.ConfigureForUnixVisitor" project="acyclic-visitor" 
-    file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitor.java" binary="false" 
-    corner="BOTTOM_RIGHT">    
-    <position height="124" width="196" x="647" y="225"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <class id="4" language="java" name="com.iluwatar.acyclicvisitor.Zoom" project="acyclic-visitor" 
-    file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Zoom.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="203" y="305"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <interface id="5" language="java" name="com.iluwatar.acyclicvisitor.HayesVisitor" project="acyclic-visitor" 
-    file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/HayesVisitor.java" binary="false" 
-    corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="1019" y="468"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </interface>  
-  <interface id="6" language="java" name="com.iluwatar.acyclicvisitor.ZoomVisitor" project="acyclic-visitor" 
-    file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ZoomVisitor.java" binary="false" 
-    corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="758" y="467"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </interface>  
-  <class id="7" language="java" name="com.iluwatar.acyclicvisitor.Hayes" project="acyclic-visitor" 
-    file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Hayes.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="479" y="307"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <class id="8" language="java" name="com.iluwatar.acyclicvisitor.ConfigureForDosVisitor" project="acyclic-visitor" 
-    file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitor.java" binary="false" 
-    corner="BOTTOM_RIGHT">    
-    <position height="142" width="192" x="883" y="225"/>    
-    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-      sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
-      <operations public="true" package="true" protected="true" private="true" static="true"/>    
-    </display>  
-  </class>  
-  <generalization id="9">    
-    <end type="SOURCE" refId="7"/>    
-    <end type="TARGET" refId="2"/>  
-  </generalization>  
-  <realization id="10">    
-    <end type="SOURCE" refId="8"/>    
-    <end type="TARGET" refId="6"/>  
-  </realization>  
-  <realization id="11">    
-    <end type="SOURCE" refId="8"/>    
-    <end type="TARGET" refId="5"/>  
-  </realization>  
-  <realization id="12">    
-    <end type="SOURCE" refId="3"/>    
-    <end type="TARGET" refId="6"/>  
-  </realization>  
-  <realization id="13">    
-    <end type="SOURCE" refId="3"/>    
-    <end type="TARGET" refId="1"/>  
-  </realization>  
-  <realization id="14">    
-    <end type="SOURCE" refId="8"/>    
-    <end type="TARGET" refId="1"/>  
-  </realization>  
-  <generalization id="15">    
-    <end type="SOURCE" refId="4"/>    
-    <end type="TARGET" refId="2"/>  
-  </generalization>  
-  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
-    sort-features="false" accessors="true" visibility="true">    
-    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
-    <operations public="true" package="true" protected="true" private="true" static="true"/>  
-  </classifier-display>  
-  <association-display labels="true" multiplicity="true"/>
-</class-diagram>

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

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

adapter/README.md

@@ -12,9 +12,8 @@ tags:
 Wrapper
 
 ## Intent
-Convert the interface of a class into another interface the clients
-expect. Adapter lets classes work together that couldn't otherwise because of
-incompatible interfaces.
+Convert the interface of a class into another interface the clients expect. Adapter lets classes work together that 
+couldn't otherwise because of incompatible interfaces.
 
 ## Explanation
 

aggregator-microservices/README.md

@@ -6,20 +6,97 @@ permalink: /patterns/aggregator-microservices/
 categories: Architectural
 tags:
 - Cloud distributed
+- Decoupling
+- Microservices
 ---
 
 ## Intent
 
-The user makes a single call to the Aggregator, and the aggregator then calls each relevant microservice and collects
-the data, apply business logic to it, and further publish is as a REST Endpoint.
-More variations of the aggregator are: 
-- Proxy Microservice Design Pattern: A different microservice is called upon the business need. 
-- Chained Microservice Design Pattern: In this case each microservice is dependent/ chained to a series 
-of other microservices.
+The user makes a single call to the aggregator service, and the aggregator then calls each relevant microservice.
+
+## Explanation
+
+Real world example
+
+> Our web marketplace needs information about products and their current inventory. It makes a call to an aggregator
+> service which in turn calls the product information microservice and product inventory microservice returning the
+> combined information. 
+
+In plain words
+
+> Aggregator Microservice collects pieces of data from various microservices and returns an aggregate for processing. 
+
+Stack Overflow says
+
+> Aggregator Microservice invokes multiple services to achieve the functionality required by the application.
+
+**Programmatic Example**
+
+Let's start from the data model. Here's our `Product`.
+
+```java
+public class Product {
+  private String title;
+  private int productInventories;
+  // getters and setters ->
+  ...
+}
+```
+
+Next we can introduce our `Aggregator` microservice. It contains clients `ProductInformationClient` and
+`ProductInventoryClient` for calling respective microservices.
+
+```java
+@RestController
+public class Aggregator {
+
+  @Resource
+  private ProductInformationClient informationClient;
+
+  @Resource
+  private ProductInventoryClient inventoryClient;
+
+  @RequestMapping(path = "/product", method = RequestMethod.GET)
+  public Product getProduct() {
+
+    var product = new Product();
+    var productTitle = informationClient.getProductTitle();
+    var productInventory = inventoryClient.getProductInventories();
+
+    //Fallback to error message
+    product.setTitle(requireNonNullElse(productTitle, "Error: Fetching Product Title Failed"));
+
+    //Fallback to default error inventory
+    product.setProductInventories(requireNonNullElse(productInventory, -1));
+
+    return product;
+  }
+}
+```
+
+Here's the essence of information microservice implementation. Inventory microservice is similar, it just returns
+inventory counts.
+
+```java
+@RestController
+public class InformationController {
+  @RequestMapping(value = "/information", method = RequestMethod.GET)
+  public String getProductTitle() {
+    return "The Product Title.";
+  }
+}
+```
+
+Now calling our `Aggregator` REST API returns the product information.
+
+```bash
+curl http://localhost:50004/product
+{"title":"The Product Title.","productInventories":5}
+```
 
 ## Class diagram
 
-![alt text](./etc/aggregator-microservice.png "Aggregator Microservice")
+![alt text](./aggregator-service/etc/aggregator-service.png "Aggregator Microservice")
 
 ## Applicability
 
@@ -28,3 +105,5 @@ Use the Aggregator Microservices pattern when you need a unified API for various
 ## Credits
 
 * [Microservice Design Patterns](http://web.archive.org/web/20190705163602/http://blog.arungupta.me/microservice-design-patterns/)
+* [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=8b4e570267bc5fb8b8189917b461dc60)
+* [Architectural Patterns: Uncover essential patterns in the most indispensable realm of enterprise architecture](https://www.amazon.com/gp/product/B077T7V8RC/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=B077T7V8RC&linkId=c34d204bfe1b277914b420189f09c1a4)

ambassador/README.md

@@ -10,28 +10,37 @@ tags:
 ---
 
 ## Intent
+
 Provide a helper service instance on a client and offload common functionality away from a shared resource.
 
 ## Explanation
+
 Real world example
 
-> A remote service has many clients accessing a function it provides. The service is a legacy application and is impossible to update. Large numbers of requests from users are causing connectivity issues. New rules for request frequency should be implemented along with latency checks and client-side logging.
+> A remote service has many clients accessing a function it provides. The service is a legacy application and is 
+> impossible to update. Large numbers of requests from users are causing connectivity issues. New rules for request 
+> frequency should be implemented along with latency checks and client-side logging.
 
 In plain words
 
-> Using the ambassador pattern, we can implement less-frequent polling from clients along with latency checks and logging.
+> With the Ambassador pattern, we can implement less-frequent polling from clients along with latency checks and 
+> logging.
 
 Microsoft documentation states
 
-> 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.
+> An ambassador service can be thought of as an out-of-process proxy which 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.
 
 **Programmatic Example**
 
-With the above example in mind we will imitate the functionality in a simple manner. We have an interface implemented by the remote service as well as the ambassador service:
+With the above introduction in mind we will imitate the functionality in this example. We have an interface implemented 
+by the remote service as well as the ambassador service:
 
 ```java
 interface RemoteServiceInterface {
-
     long doRemoteFunction(int value) throws Exception;
 }
 ```
@@ -136,7 +145,7 @@ public class Client {
 }
 ```
 
-And here are two clients using the service.
+Here are two clients using the service.
 
 ```java
 public class App {
@@ -149,13 +158,29 @@ public class App {
 }
 ```
 
+Here's the output for running the example:
+
+```java
+Time taken (ms): 111
+Service result: 120
+Time taken (ms): 931
+Failed to reach remote: (1)
+Time taken (ms): 665
+Failed to reach remote: (2)
+Time taken (ms): 538
+Failed to reach remote: (3)
+Service result: -1
+```
+
 ## 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
-be implemented on the client avoiding the need for changes on the remote service.
+
+Ambassador is applicable when working with a legacy remote service which cannot be modified or would be extremely 
+difficult to modify. Connectivity features can be implemented on the client avoiding the need for changes on the remote 
+service.
 
 * Ambassador provides a local interface for a remote service.
 * Ambassador provides logging, circuit breaking, retries and security on the client.
@@ -168,10 +193,14 @@ be implemented on the client avoiding the need for changes on the remote service
 * Offload remote service tasks
 * Facilitate network connection
 
-## Real world examples
+## Known uses
 
 * [Kubernetes-native API gateway for microservices](https://github.com/datawire/ambassador)
 
+## Related patterns
+
+* [Proxy](https://java-design-patterns.com/patterns/proxy/)
+
 ## Credits
 
 * [Ambassador pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/ambassador)

ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java

@@ -29,5 +29,5 @@ package com.iluwatar.ambassador;
 interface RemoteServiceInterface {
   int FAILURE = -1;
 
-  long doRemoteFunction(int value) throws Exception;
+  long doRemoteFunction(int value);
 }

api-gateway/README.md

@@ -12,49 +12,53 @@ tags:
 
 ## Intent
 
-Aggregate calls to microservices in a single location: the API Gateway. The user makes a single call to the API Gateway, 
-and the API Gateway then calls each relevant microservice.
+Aggregate calls to microservices in a single location, the API Gateway. The user makes a single call 
+to the API Gateway, 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 
+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.
+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.
+> 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. 
+> 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.
+> 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`.
+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.
 
@@ -64,7 +68,6 @@ public interface ImageClient {
 }
 
 public class ImageClientImpl implements ImageClient {
-
   @Override
   public String getImagePath() {
     var httpClient = HttpClient.newHttpClient();
@@ -114,7 +117,7 @@ public class PriceClientImpl implements PriceClient {
 }
 ```
 
-And here we can see how API Gateway maps the requests to the microservices.
+Here we can see how API Gateway maps the requests to the microservices.
 
 ```java
 public class ApiGateway {

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java

@@ -23,11 +23,16 @@
 
 package com.iluwatar.api.gateway;
 
+import static org.slf4j.LoggerFactory.getLogger;
+
 import java.io.IOException;
 import java.net.URI;
 import java.net.http.HttpClient;
 import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
 import java.net.http.HttpResponse.BodyHandlers;
+
+import org.slf4j.Logger;
 import org.springframework.stereotype.Component;
 
 /**
@@ -35,6 +40,8 @@ import org.springframework.stereotype.Component;
  */
 @Component
 public class ImageClientImpl implements ImageClient {
+  private static final Logger LOGGER = getLogger(ImageClientImpl.class);
+
   /**
    * Makes a simple HTTP Get request to the Image microservice.
    *
@@ -49,12 +56,26 @@ public class ImageClientImpl implements ImageClient {
         .build();
 
     try {
+      LOGGER.info("Sending request to fetch image path");
       var httpResponse = httpClient.send(httpGet, BodyHandlers.ofString());
+      logResponse(httpResponse);
       return httpResponse.body();
     } catch (IOException | InterruptedException e) {
-      e.printStackTrace();
+      LOGGER.error("Failure occurred while getting image path", e);
     }
 
     return null;
   }
+
+  private void logResponse(HttpResponse<String> httpResponse) {
+    if (isSuccessResponse(httpResponse.statusCode())) {
+      LOGGER.info("Image path received successfully");
+    } else {
+      LOGGER.warn("Image path request failed");
+    }
+  }
+
+  private boolean isSuccessResponse(int responseCode) {
+    return responseCode >= 200 && responseCode <= 299;
+  }
 }

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java

@@ -23,18 +23,26 @@
 
 package com.iluwatar.api.gateway;
 
+import static org.slf4j.LoggerFactory.getLogger;
+
 import java.io.IOException;
 import java.net.URI;
 import java.net.http.HttpClient;
 import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
 import java.net.http.HttpResponse.BodyHandlers;
+
+import org.slf4j.Logger;
 import org.springframework.stereotype.Component;
 
+
 /**
  * An adapter to communicate with the Price microservice.
  */
 @Component
 public class PriceClientImpl implements PriceClient {
+  private static final Logger LOGGER = getLogger(PriceClientImpl.class);
+
   /**
    * Makes a simple HTTP Get request to the Price microservice.
    *
@@ -49,12 +57,26 @@ public class PriceClientImpl implements PriceClient {
         .build();
 
     try {
+      LOGGER.info("Sending request to fetch price info");
       var httpResponse = httpClient.send(httpGet, BodyHandlers.ofString());
+      logResponse(httpResponse);
       return httpResponse.body();
     } catch (IOException | InterruptedException e) {
-      e.printStackTrace();
+      LOGGER.error("Failure occurred while getting price info", e);
     }
 
     return null;
   }
+
+  private void logResponse(HttpResponse<String> httpResponse) {
+    if (isSuccessResponse(httpResponse.statusCode())) {
+      LOGGER.info("Price info received successfully");
+    } else {
+      LOGGER.warn("Price info request failed");
+    }
+  }
+
+  private boolean isSuccessResponse(int responseCode) {
+    return responseCode >= 200 && responseCode <= 299;
+  }
 }

api-gateway/image-microservice/src/main/java/com/iluwatar/image/microservice/ImageController.java

@@ -23,15 +23,20 @@
 
 package com.iluwatar.image.microservice;
 
+import static org.slf4j.LoggerFactory.getLogger;
+
+import org.slf4j.Logger;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RestController;
 
+
 /**
  * Exposes the Image microservice's endpoints.
  */
 @RestController
 public class ImageController {
+  private static final Logger LOGGER = getLogger(ImageController.class);
 
   /**
    * An endpoint for a user to retrieve an image path.
@@ -40,6 +45,7 @@ public class ImageController {
    */
   @RequestMapping(value = "/image-path", method = RequestMethod.GET)
   public String getImagePath() {
+    LOGGER.info("Successfully found image path");
     return "/product-image.png";
   }
 }

api-gateway/price-microservice/src/main/java/com/iluwatar/price/microservice/PriceController.java

@@ -23,15 +23,20 @@
 
 package com.iluwatar.price.microservice;
 
+import static org.slf4j.LoggerFactory.getLogger;
+
+import org.slf4j.Logger;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RestController;
 
+
 /**
  * Exposes the Price microservice's endpoints.
  */
 @RestController
 public class PriceController {
+  private static final Logger LOGGER = getLogger(PriceController.class);
 
   /**
    * An endpoint for a user to retrieve a product's price.
@@ -40,6 +45,7 @@ public class PriceController {
    */
   @RequestMapping(value = "/price", method = RequestMethod.GET)
   public String getPrice() {
+    LOGGER.info("Successfully found price info");
     return "20";
   }
 }

arrange-act-assert/README.md

@@ -9,22 +9,137 @@ tags:
 ---
 
 ## Also known as
+
 Given/When/Then
 
 ## Intent
-The Arrange/Act/Assert (AAA) is a pattern for organizing unit tests.
+
+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.
 
+## Explanation
+
+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.
+
+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. It makes tests more natural to write at
+the same time since you already have an outline.
+
+Real world example
+
+> We need to write comprehensive and clear unit test suite for a class.
+
+In plain words
+
+> Arrange/Act/Assert is a testing pattern that organizes tests into three clear steps for easy
+> maintenance.
+
+WikiWikiWeb says
+
+> Arrange/Act/Assert is a pattern for arranging and formatting code in UnitTest methods. 
+
+**Programmatic Example**
+
+Let's first introduce our `Cash` class to be unit tested.
+
+```java
+public class Cash {
+
+  private int amount;
+
+  Cash(int amount) {
+    this.amount = amount;
+  }
+
+  void plus(int addend) {
+    amount += addend;
+  }
+
+  boolean minus(int subtrahend) {
+    if (amount >= subtrahend) {
+      amount -= subtrahend;
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  int count() {
+    return amount;
+  }
+}
+```
+
+Then we write our unit tests according to Arrange/Act/Assert pattern. Notice the clearly
+separated steps for each unit test.
+
+```java
+public class CashAAATest {
+
+  @Test
+  public void testPlus() {
+    //Arrange
+    var cash = new Cash(3);
+    //Act
+    cash.plus(4);
+    //Assert
+    assertEquals(7, cash.count());
+  }
+
+  @Test
+  public void testMinus() {
+    //Arrange
+    var cash = new Cash(8);
+    //Act
+    var result = cash.minus(5);
+    //Assert
+    assertTrue(result);
+    assertEquals(3, cash.count());
+  }
+
+  @Test
+  public void testInsufficientMinus() {
+    //Arrange
+    var cash = new Cash(1);
+    //Act
+    var result = cash.minus(6);
+    //Assert
+    assertFalse(result);
+    assertEquals(1, cash.count());
+  }
+
+  @Test
+  public void testUpdate() {
+    //Arrange
+    var cash = new Cash(5);
+    //Act
+    cash.plus(6);
+    var result = cash.minus(3);
+    //Assert
+    assertTrue(result);
+    assertEquals(8, cash.count());
+  }
+}
+```
+
 ## Applicability
+
 Use Arrange/Act/Assert pattern when
 
-* you need to structure your unit tests so they're easier to read, maintain, and enhance. 
+* You need to structure your unit tests so that 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)
+* [xUnit Test Patterns: Refactoring Test Code](https://www.amazon.com/gp/product/0131495054/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=0131495054&linkId=99701e8f4af2f7e8dd50d720c9b63dbf)
+* [Unit Testing Principles, Practices, and Patterns](https://www.amazon.com/gp/product/1617296279/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=1617296279&linkId=74c75cf22a63c3e4758ae08aa0a0cc35)
+* [Test Driven Development: By Example](https://www.amazon.com/gp/product/0321146530/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=0321146530&linkId=5c63a93d8c1175b84ca5087472ef0e05)

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

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

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

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

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

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

command/README.md

@@ -75,19 +75,18 @@ public class Wizard {
 Next we present the spell hierarchy.
 
 ```java
-public abstract class Command {
+public interface Command {
 
-  public abstract void execute(Target target);
+  void execute(Target target);
 
-  public abstract void undo();
+  void undo();
 
-  public abstract void redo();
+  void redo();
 
-  @Override
-  public abstract String toString();
+  String toString();
 }
 
-public class InvisibilitySpell extends Command {
+public class InvisibilitySpell implements Command {
 
   private Target target;
 
@@ -117,7 +116,7 @@ public class InvisibilitySpell extends Command {
   }
 }
 
-public class ShrinkSpell extends Command {
+public class ShrinkSpell implements Command {
 
   private Size oldSize;
   private Target target;

command/etc/command.urm.puml

@@ -4,7 +4,7 @@ package com.iluwatar.command {
     + App()
     + main(args : String[]) {static}
   }
-  abstract class Command {
+  interface Command {
     + Command()
     + execute(Target) {abstract}
     + redo() {abstract}
@@ -77,7 +77,7 @@ ShrinkSpell -->  "-oldSize" Size
 InvisibilitySpell -->  "-target" Target
 ShrinkSpell -->  "-target" Target
 Target -->  "-visibility" Visibility
-Goblin --|> Target 
-InvisibilitySpell --|> Command 
-ShrinkSpell --|> Command 
-@enduml
+Goblin --|> Target
+InvisibilitySpell ..|> Command
+ShrinkSpell ..|> Command
+@enduml

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

@@ -26,15 +26,12 @@ package com.iluwatar.command;
 /**
  * Interface for Commands.
  */
-public abstract class Command {
+public interface Command {
+  void execute(Target target);
 
-  public abstract void execute(Target target);
+  void undo();
 
-  public abstract void undo();
-
-  public abstract void redo();
-
-  @Override
-  public abstract String toString();
+  void redo();
 
+  String toString();
 }

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

@@ -26,7 +26,7 @@ package com.iluwatar.command;
 /**
  * InvisibilitySpell is a concrete command.
  */
-public class InvisibilitySpell extends Command {
+public class InvisibilitySpell implements Command {
 
   private Target target;
 

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

@@ -26,7 +26,7 @@ package com.iluwatar.command;
 /**
  * ShrinkSpell is a concrete command.
  */
-public class ShrinkSpell extends Command {
+public class ShrinkSpell implements Command {
 
   private Size oldSize;
   private Target target;

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

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

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

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

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

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

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

@@ -1,29 +0,0 @@
-/*
- * 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.
- */
-
-module com.iluwatar.dao {
-	requires org.slf4j;
-	requires java.sql;
-	requires h2;
-	requires java.naming;
-}

data-mapper/src/main/java/com/iluwatar/datamapper/module-info.java

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

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

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

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

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

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

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

dirty-flag/src/main/java/com/iluwatar/dirtyflag/module-info.java

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

double-checked-locking/src/main/java/com/iluwatar/doublechecked/locking/module-info.java

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

double-dispatch/src/main/java/com/iluwatar/doubledispatch/module-info.java

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

eip-message-channel/src/main/java/com/iluwatar/eip/message/channel/module-info.java

@@ -1,27 +0,0 @@
-/*
- * 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.
- */
-
-module com.iluwatar.eipmessagechannel {
-	requires org.slf4j;
-	requires camel.core;
-}

eip-publish-subscribe/src/main/java/com/iluwatar/eip/publish/subscribe/module-info.java

@@ -1,27 +0,0 @@
-/*
- * 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.
- */
-
-module com.iluwatar.eippublishsubscribe {
-	requires org.slf4j;
-	requires camel.core;
-}

event-aggregator/src/main/java/com/iluwatar/event/aggregator/module-info.java

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

event-asynchronous/src/main/java/com/iluwatar/event/asynchronous/module-info.java

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

execute-around/src/main/java/com/iluwatar/execute/around/module-info.java

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

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

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

factory-kit/src/main/java/com/iluwatar/factorykit/module-info.java

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

factory-method/src/main/java/com/iluwatar/factory/method/module-info.java

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

feature-toggle/src/main/java/com/iluwatar/featuretoggle/module-info.java

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

marker/src/main/java/App.java

@@ -46,17 +46,18 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
+    final var logger = LoggerFactory.getLogger(App.class);
+    var guard = new Guard();
+    var thief = new Thief();
 
-    final Logger logger = LoggerFactory.getLogger(App.class);
-    Guard guard = new Guard();
-    Thief thief = new Thief();
-
+    //noinspection ConstantConditions
     if (guard instanceof Permission) {
       guard.enter();
     } else {
       logger.info("You have no permission to enter, please leave this area");
     }
 
+    //noinspection ConstantConditions
     if (thief instanceof Permission) {
       thief.steal();
     } else {

marker/src/main/java/Guard.java

@@ -28,11 +28,9 @@ import org.slf4j.LoggerFactory;
  * Class defining Guard.
  */
 public class Guard implements Permission {
-
   private static final Logger LOGGER = LoggerFactory.getLogger(Guard.class);
 
-  protected static void enter() {
-
+  protected void enter() {
     LOGGER.info("You can enter");
   }
 }

marker/src/main/java/Thief.java

@@ -28,14 +28,13 @@ import org.slf4j.LoggerFactory;
  * Class defining Thief.
  */
 public class Thief {
-
   private static final Logger LOGGER = LoggerFactory.getLogger(Thief.class);
 
-  protected static void steal() {
+  protected void steal() {
     LOGGER.info("Steal valuable items");
   }
 
-  protected static void doNothing() {
+  protected void doNothing() {
     LOGGER.info("Pretend nothing happened and just leave");
   }
 }

marker/src/test/java/AppTest.java

@@ -30,7 +30,6 @@ public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 }

marker/src/test/java/GuardTest.java

@@ -33,7 +33,7 @@ public class GuardTest {
 
   @Test
   public void testGuard() {
-    Guard guard = new Guard();
+    var guard = new Guard();
     assertThat(guard, instanceOf(Permission.class));
   }
 }

marker/src/test/java/ThiefTest.java

@@ -21,9 +21,11 @@
  * THE SOFTWARE.
  */
 
-import org.junit.jupiter.api.Test;
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.hamcrest.CoreMatchers.not;
+import static org.hamcrest.MatcherAssert.assertThat;
 
-import static org.junit.jupiter.api.Assertions.assertFalse;
+import org.junit.jupiter.api.Test;
 
 /**
  * Thief test
@@ -31,7 +33,7 @@ import static org.junit.jupiter.api.Assertions.assertFalse;
 public class ThiefTest {
   @Test
   public void testThief() {
-    Thief thief = new Thief();
-    assertFalse(thief instanceof Permission);
+    var thief = new Thief();
+    assertThat(thief, not(instanceOf(Permission.class)));
   }
 }

master-worker-pattern/pom.xml

@@ -22,38 +22,39 @@
     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>1.23.0-SNAPSHOT</version>
-  </parent>
-  <artifactId>master-worker-pattern</artifactId>
-  <dependencies>
-      <dependency>
-          <groupId>org.junit.jupiter</groupId>
-          <artifactId>junit-jupiter-engine</artifactId>
-          <scope>test</scope>
-      </dependency>
+<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>1.23.0-SNAPSHOT</version>
+    </parent>
+    <artifactId>master-worker-pattern</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.masterworker.App</mainClass>
-                </manifest>
-              </archive>
-            </configuration>
-          </execution>
-        </executions>
-      </plugin>
-    </plugins>
-  </build>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <configuration>
+                            <archive>
+                                <manifest>
+                                    <mainClass>com.iluwatar.masterworker.App</mainClass>
+                                </manifest>
+                            </archive>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
 </project>

master-worker-pattern/src/main/java/com/iluwatar/masterworker/App.java

@@ -34,27 +34,25 @@ import org.slf4j.LoggerFactory;
 
 /**
  * <p>The <b><em>Master-Worker</em></b> pattern is used when the problem at hand can be solved by
- * dividing into
- * multiple parts which need to go through the same computation and may need to be aggregated to get
- * final result. Parallel processing is performed using a system consisting of a master and some
- * number of workers, where a master divides the work among the workers, gets the result back from
- * them and assimilates all the results to give final result. The only communication is between the
- * master and the worker - none of the workers communicate among one another and the user only
- * communicates with the master to get required job done.</p>
+ * dividing into multiple parts which need to go through the same computation and may need to be
+ * aggregated to get final result. Parallel processing is performed using a system consisting of a
+ * master and some number of workers, where a master divides the work among the workers, gets the
+ * result back from them and assimilates all the results to give final result. The only
+ * communication is between the master and the worker - none of the workers communicate among one
+ * another and the user only communicates with the master to get required job done.</p>
  * <p>In our example, we have generic abstract classes {@link MasterWorker}, {@link Master} and
- * {@link Worker} which
- * have to be extended by the classes which will perform the specific job at hand (in this case
- * finding transpose of matrix, done by {@link ArrayTransposeMasterWorker}, {@link
- * ArrayTransposeMaster} and {@link ArrayTransposeWorker}). The Master class divides the work into
- * parts to be given to the workers, collects the results from the workers and aggregates it when
- * all workers have responded before returning the solution. The Worker class extends the Thread
- * class to enable parallel processing, and does the work once the data has been received from the
- * Master. The MasterWorker contains a reference to the Master class, gets the input from the App
- * and passes it on to the Master. These 3 classes define the system which computes the result. We
- * also have 2 abstract classes {@link Input} and {@link Result}, which contain the input data and
- * result data respectively. The Input class also has an abstract method divideData which defines
- * how the data is to be divided into segments. These classes are extended by {@link ArrayInput} and
- * {@link ArrayResult}.</p>
+ * {@link Worker} which have to be extended by the classes which will perform the specific job at
+ * hand (in this case finding transpose of matrix, done by {@link ArrayTransposeMasterWorker},
+ * {@link ArrayTransposeMaster} and {@link ArrayTransposeWorker}). The Master class divides the work
+ * into parts to be given to the workers, collects the results from the workers and aggregates it
+ * when all workers have responded before returning the solution. The Worker class extends the
+ * Thread class to enable parallel processing, and does the work once the data has been received
+ * from the Master. The MasterWorker contains a reference to the Master class, gets the input from
+ * the App and passes it on to the Master. These 3 classes define the system which computes the
+ * result. We also have 2 abstract classes {@link Input} and {@link Result}, which contain the input
+ * data and result data respectively. The Input class also has an abstract method divideData which
+ * defines how the data is to be divided into segments. These classes are extended by {@link
+ * ArrayInput} and {@link ArrayResult}.</p>
  */
 
 public class App {
@@ -68,12 +66,12 @@ public class App {
    */
 
   public static void main(String[] args) {
-    ArrayTransposeMasterWorker mw = new ArrayTransposeMasterWorker();
-    int rows = 10;
-    int columns = 20;
-    int[][] inputMatrix = ArrayUtilityMethods.createRandomIntMatrix(rows, columns);
-    ArrayInput input = new ArrayInput(inputMatrix);
-    ArrayResult result = (ArrayResult) mw.getResult(input);
+    var mw = new ArrayTransposeMasterWorker();
+    var rows = 10;
+    var columns = 20;
+    var inputMatrix = ArrayUtilityMethods.createRandomIntMatrix(rows, columns);
+    var input = new ArrayInput(inputMatrix);
+    var result = (ArrayResult) mw.getResult(input);
     if (result != null) {
       ArrayUtilityMethods.printMatrix(inputMatrix);
       ArrayUtilityMethods.printMatrix(result.data);

master-worker-pattern/src/main/java/com/iluwatar/masterworker/ArrayInput.java

@@ -25,6 +25,7 @@ package com.iluwatar.masterworker;
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.List;
 
 /**
  * Class ArrayInput extends abstract class {@link Input} and contains data of type int[][].
@@ -37,12 +38,12 @@ public class ArrayInput extends Input<int[][]> {
   }
 
   static int[] makeDivisions(int[][] data, int num) {
-    int initialDivision = data.length / num; //equally dividing
-    int[] divisions = new int[num];
+    var initialDivision = data.length / num; //equally dividing
+    var divisions = new int[num];
     Arrays.fill(divisions, initialDivision);
     if (initialDivision * num != data.length) {
-      int extra = data.length - initialDivision * num;
-      int l = 0;
+      var extra = data.length - initialDivision * num;
+      var l = 0;
       //equally dividing extra among all parts
       while (extra > 0) {
         divisions[l] = divisions[l] + 1;
@@ -58,22 +59,20 @@ public class ArrayInput extends Input<int[][]> {
   }
 
   @Override
-  public ArrayList<Input> divideData(int num) {
+  public List<Input<int[][]>> divideData(int num) {
     if (this.data == null) {
       return null;
     } else {
-      int[] divisions = makeDivisions(this.data, num);
-      ArrayList<Input> result = new ArrayList<Input>(num);
-      int rowsDone = 0; //number of rows divided so far
-      for (int i = 0; i < num; i++) {
-        int rows = divisions[i];
+      var divisions = makeDivisions(this.data, num);
+      var result = new ArrayList<Input<int[][]>>(num);
+      var rowsDone = 0; //number of rows divided so far
+      for (var i = 0; i < num; i++) {
+        var rows = divisions[i];
         if (rows != 0) {
-          int[][] divided = new int[rows][this.data[0].length];
-          for (int j = 0; j < rows; j++) {
-            divided[j] = this.data[rowsDone + j];
-          }
+          var divided = new int[rows][this.data[0].length];
+          System.arraycopy(this.data, rowsDone, divided, 0, rows);
           rowsDone += rows;
-          ArrayInput dividedInput = new ArrayInput(divided);
+          var dividedInput = new ArrayInput(divided);
           result.add(dividedInput);
         } else {
           break; //rest of divisions will also be 0

master-worker-pattern/src/main/java/com/iluwatar/masterworker/ArrayUtilityMethods.java

@@ -47,8 +47,8 @@ public class ArrayUtilityMethods {
     if (a1.length != a2.length) {
       return false;
     } else {
-      boolean answer = false;
-      for (int i = 0; i < a1.length; i++) {
+      var answer = false;
+      for (var i = 0; i < a1.length; i++) {
         if (a1[i] == a2[i]) {
           answer = true;
         } else {
@@ -69,8 +69,8 @@ public class ArrayUtilityMethods {
     if (m1.length != m2.length) {
       return false;
     } else {
-      boolean answer = false;
-      for (int i = 0; i < m1.length; i++) {
+      var answer = false;
+      for (var i = 0; i < m1.length; i++) {
         if (arraysSame(m1[i], m2[i])) {
           answer = true;
         } else {
@@ -88,9 +88,9 @@ public class ArrayUtilityMethods {
    * @return it (int[][]).
    */
   public static int[][] createRandomIntMatrix(int rows, int columns) {
-    int[][] matrix = new int[rows][columns];
-    for (int i = 0; i < rows; i++) {
-      for (int j = 0; j < columns; j++) {
+    var matrix = new int[rows][columns];
+    for (var i = 0; i < rows; i++) {
+      for (var j = 0; j < columns; j++) {
         //filling cells in matrix
         matrix[i][j] = RANDOM.nextInt(10);
       }
@@ -104,9 +104,9 @@ public class ArrayUtilityMethods {
 
   public static void printMatrix(int[][] matrix) {
     //prints out int[][]
-    for (int i = 0; i < matrix.length; i++) {
-      for (int j = 0; j < matrix[0].length; j++) {
-        LOGGER.info(matrix[i][j] + " ");
+    for (var ints : matrix) {
+      for (var j = 0; j < matrix[0].length; j++) {
+        LOGGER.info(ints[j] + " ");
       }
       LOGGER.info("");
     }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/Input.java

@@ -23,7 +23,7 @@
 
 package com.iluwatar.masterworker;
 
-import java.util.ArrayList;
+import java.util.List;
 
 /**
  * The abstract Input class, having 1 public field which contains input data, and abstract method
@@ -40,5 +40,5 @@ public abstract class Input<T> {
     this.data = data;
   }
 
-  public abstract ArrayList<Input> divideData(int num);
+  public abstract List<Input<T>> divideData(int num);
 }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/MasterWorker.java

@@ -40,7 +40,7 @@ public abstract class MasterWorker {
 
   abstract Master setMaster(int numOfWorkers);
 
-  public Result getResult(Input input) {
+  public Result<?> getResult(Input<?> input) {
     this.master.doWork(input);
     return this.master.getFinalResult();
   }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/systemmaster/ArrayTransposeMaster.java

@@ -27,7 +27,8 @@ import com.iluwatar.masterworker.ArrayResult;
 import com.iluwatar.masterworker.system.systemworkers.ArrayTransposeWorker;
 import com.iluwatar.masterworker.system.systemworkers.Worker;
 import java.util.ArrayList;
-import java.util.Enumeration;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 
 /**
  * Class ArrayTransposeMaster extends abstract class {@link Master} and contains definition of
@@ -41,35 +42,33 @@ public class ArrayTransposeMaster extends Master {
 
   @Override
   ArrayList<Worker> setWorkers(int num) {
-    ArrayList<Worker> ws = new ArrayList<Worker>(num);
-    for (int i = 0; i < num; i++) {
-      ws.add(new ArrayTransposeWorker(this, i + 1));
-      //i+1 will be id
-    }
-    return ws;
+    //i+1 will be id
+    return IntStream.range(0, num)
+        .mapToObj(i -> new ArrayTransposeWorker(this, i + 1))
+        .collect(Collectors.toCollection(() -> new ArrayList<>(num)));
   }
 
   @Override
   ArrayResult aggregateData() {
     // number of rows in final result is number of rows in any of obtained results from workers
-    int rows = ((ArrayResult) this.getAllResultData()
-        .get(this.getAllResultData().keys().nextElement())).data.length;
-    int columns =
-        0; //number of columns is sum of number of columns in all results obtained from workers
-    for (Enumeration<Integer> e = this.getAllResultData().keys(); e.hasMoreElements(); ) {
-      columns += ((ArrayResult) this.getAllResultData().get(e.nextElement())).data[0].length;
+    var allResultData = this.getAllResultData();
+    var rows = ((ArrayResult) allResultData.elements().nextElement()).data.length;
+    var elements = allResultData.elements();
+    var columns = 0; // columns = sum of number of columns in all results obtained from workers
+    while (elements.hasMoreElements()) {
+      columns += ((ArrayResult) elements.nextElement()).data[0].length;
     }
-    int[][] resultData = new int[rows][columns];
-    int columnsDone = 0; //columns aggregated so far
-    for (int i = 0; i < this.getExpectedNumResults(); i++) {
+    var resultData = new int[rows][columns];
+    var columnsDone = 0; //columns aggregated so far
+    var workers = this.getWorkers();
+    for (var i = 0; i < this.getExpectedNumResults(); i++) {
       //result obtained from ith worker
-      int[][] work =
-          ((ArrayResult) this.getAllResultData().get(this.getWorkers().get(i).getWorkerId())).data;
-      for (int m = 0; m < work.length; m++) {
+      var worker = workers.get(i);
+      var workerId = worker.getWorkerId();
+      var work = ((ArrayResult) allResultData.get(workerId)).data;
+      for (var m = 0; m < work.length; m++) {
         //m = row number, n = columns number
-        for (int n = 0; n < work[0].length; n++) {
-          resultData[m][columnsDone + n] = work[m][n];
-        }
+        System.arraycopy(work[m], 0, resultData[m], columnsDone, work[0].length);
       }
       columnsDone += work[0].length;
     }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/systemmaster/Master.java

@@ -26,8 +26,8 @@ package com.iluwatar.masterworker.system.systemmaster;
 import com.iluwatar.masterworker.Input;
 import com.iluwatar.masterworker.Result;
 import com.iluwatar.masterworker.system.systemworkers.Worker;
-import java.util.ArrayList;
 import java.util.Hashtable;
+import java.util.List;
 
 /**
  * The abstract Master class which contains private fields numOfWorkers (number of workers), workers
@@ -38,24 +38,24 @@ import java.util.Hashtable;
 
 public abstract class Master {
   private final int numOfWorkers;
-  private final ArrayList<Worker> workers;
+  private final List<Worker> workers;
+  private final Hashtable<Integer, Result<?>> allResultData;
   private int expectedNumResults;
-  private final Hashtable<Integer, Result> allResultData;
-  private Result finalResult;
+  private Result<?> finalResult;
 
   Master(int numOfWorkers) {
     this.numOfWorkers = numOfWorkers;
     this.workers = setWorkers(numOfWorkers);
     this.expectedNumResults = 0;
-    this.allResultData = new Hashtable<Integer, Result>(numOfWorkers);
+    this.allResultData = new Hashtable<>(numOfWorkers);
     this.finalResult = null;
   }
 
-  public Result getFinalResult() {
+  public Result<?> getFinalResult() {
     return this.finalResult;
   }
 
-  Hashtable<Integer, Result> getAllResultData() {
+  Hashtable<Integer, Result<?>> getAllResultData() {
     return this.allResultData;
   }
 
@@ -63,34 +63,41 @@ public abstract class Master {
     return this.expectedNumResults;
   }
 
-  ArrayList<Worker> getWorkers() {
+  List<Worker> getWorkers() {
     return this.workers;
   }
 
-  abstract ArrayList<Worker> setWorkers(int num);
+  abstract List<Worker> setWorkers(int num);
 
-  public void doWork(Input input) {
+  public void doWork(Input<?> input) {
     divideWork(input);
   }
 
-  private void divideWork(Input input) {
-    ArrayList<Input> dividedInput = input.divideData(numOfWorkers);
+  private void divideWork(Input<?> input) {
+    var dividedInput = input.divideData(numOfWorkers);
     if (dividedInput != null) {
       this.expectedNumResults = dividedInput.size();
-      for (int i = 0; i < this.expectedNumResults; i++) {
+      for (var i = 0; i < this.expectedNumResults; i++) {
         //ith division given to ith worker in this.workers
         this.workers.get(i).setReceivedData(this, dividedInput.get(i));
-        this.workers.get(i).run();
+        this.workers.get(i).start();
+      }
+      for (var i = 0; i < this.expectedNumResults; i++) {
+        try {
+          this.workers.get(i).join();
+        } catch (InterruptedException e) {
+          System.err.println("Error while executing thread");
+        }
       }
     }
   }
 
-  public void receiveData(Result data, Worker w) {
+  public void receiveData(Result<?> data, Worker w) {
     //check if can receive..if yes:
     collectResult(data, w.getWorkerId());
   }
 
-  private void collectResult(Result data, int workerId) {
+  private void collectResult(Result<?> data, int workerId) {
     this.allResultData.put(workerId, data);
     if (this.allResultData.size() == this.expectedNumResults) {
       //all data received
@@ -98,5 +105,5 @@ public abstract class Master {
     }
   }
 
-  abstract Result aggregateData();
+  abstract Result<?> aggregateData();
 }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/systemworkers/ArrayTransposeWorker.java

@@ -41,12 +41,12 @@ public class ArrayTransposeWorker extends Worker {
   @Override
   ArrayResult executeOperation() {
     //number of rows in result matrix is equal to number of columns in input matrix and vice versa
-    ArrayInput arrayInput = (ArrayInput) this.getReceivedData();
-    final int rows = arrayInput.data[0].length;
-    final int cols = arrayInput.data.length;
-    int[][] resultData = new int[rows][cols];
-    for (int i = 0; i < cols; i++) {
-      for (int j = 0; j < rows; j++) {
+    var arrayInput = (ArrayInput) this.getReceivedData();
+    final var rows = arrayInput.data[0].length;
+    final var cols = arrayInput.data.length;
+    var resultData = new int[rows][cols];
+    for (var i = 0; i < cols; i++) {
+      for (var j = 0; j < rows; j++) {
         //flipping element positions along diagonal
         resultData[j][i] = arrayInput.data[i][j];
       }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/systemworkers/Worker.java

@@ -35,7 +35,7 @@ import com.iluwatar.masterworker.system.systemmaster.Master;
 public abstract class Worker extends Thread {
   private final Master master;
   private final int workerId;
-  private Input receivedData;
+  private Input<?> receivedData;
 
   Worker(Master master, int id) {
     this.master = master;
@@ -47,23 +47,23 @@ public abstract class Worker extends Thread {
     return this.workerId;
   }
 
-  Input getReceivedData() {
+  Input<?> getReceivedData() {
     return this.receivedData;
   }
 
-  public void setReceivedData(Master m, Input i) {
+  public void setReceivedData(Master m, Input<?> i) {
     //check if ready to receive..if yes:
     this.receivedData = i;
   }
 
-  abstract Result executeOperation();
+  abstract Result<?> executeOperation();
 
-  private void sendToMaster(Result data) {
+  private void sendToMaster(Result<?> data) {
     this.master.receiveData(data, this);
   }
 
   public void run() { //from Thread class
-    Result work = executeOperation();
+    var work = executeOperation();
     sendToMaster(work);
   }
 }

master-worker-pattern/src/test/java/com/iluwatar/masterworker/ArrayInputTest.java

@@ -23,38 +23,39 @@
 
 package com.iluwatar.masterworker;
 
-import static org.junit.jupiter.api.Assertions.*;
-import java.util.ArrayList;
+import static com.iluwatar.masterworker.ArrayUtilityMethods.matricesSame;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import java.util.Random;
 import org.junit.jupiter.api.Test;
 
 /**
-* Testing divideData method in {@link ArrayInput} class.
-*/
+ * Testing divideData method in {@link ArrayInput} class.
+ */
 
 class ArrayInputTest {
 
   @Test
   void divideDataTest() {
-    int rows = 10;
-    int columns = 10;
-    int[][] inputMatrix = new int[rows][columns];
-    Random rand = new Random();
-    for (int i = 0; i < rows; i++) {
-      for (int j = 0; j < columns; j++) {
+    var rows = 10;
+    var columns = 10;
+    var inputMatrix = new int[rows][columns];
+    var rand = new Random();
+    for (var i = 0; i < rows; i++) {
+      for (var j = 0; j < columns; j++) {
         inputMatrix[i][j] = rand.nextInt(10);
       }
     }
-    ArrayInput i = new ArrayInput(inputMatrix);
-    ArrayList<Input> table = i.divideData(4);
-    int[][] division1 = new int[][] {inputMatrix[0], inputMatrix[1], inputMatrix[2]};
-    int[][] division2 = new int[][] {inputMatrix[3], inputMatrix[4], inputMatrix[5]};
-    int[][] division3 = new int[][] {inputMatrix[6], inputMatrix[7]};
-    int[][] division4 = new int[][] {inputMatrix[8], inputMatrix[9]};
-    assertTrue(ArrayUtilityMethods.matricesSame((int[][]) table.get(0).data, division1) 
-            && ArrayUtilityMethods.matricesSame((int[][]) table.get(1).data, division2)
-            && ArrayUtilityMethods.matricesSame((int[][]) table.get(2).data, division3) 
-            && ArrayUtilityMethods.matricesSame((int[][]) table.get(3).data, division4));
+    var i = new ArrayInput(inputMatrix);
+    var table = i.divideData(4);
+    var division1 = new int[][]{inputMatrix[0], inputMatrix[1], inputMatrix[2]};
+    var division2 = new int[][]{inputMatrix[3], inputMatrix[4], inputMatrix[5]};
+    var division3 = new int[][]{inputMatrix[6], inputMatrix[7]};
+    var division4 = new int[][]{inputMatrix[8], inputMatrix[9]};
+    assertTrue(matricesSame(table.get(0).data, division1)
+        && matricesSame(table.get(1).data, division2)
+        && matricesSame(table.get(2).data, division3)
+        && matricesSame(table.get(3).data, division4));
   }
 
 }

master-worker-pattern/src/test/java/com/iluwatar/masterworker/ArrayUtilityMethodsTest.java

@@ -23,27 +23,27 @@
 
 package com.iluwatar.masterworker;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import org.junit.jupiter.api.Test;
 
 /**
-* Testing utility methods in {@link ArrayUtilityMethods} class.
-*/
+ * Testing utility methods in {@link ArrayUtilityMethods} class.
+ */
 
 class ArrayUtilityMethodsTest {
 
   @Test
   void arraysSameTest() {
-    int[] arr1 = new int[] {1,4,2,6};
-    int[] arr2 = new int[] {1,4,2,6};
+    var arr1 = new int[]{1, 4, 2, 6};
+    var arr2 = new int[]{1, 4, 2, 6};
     assertTrue(ArrayUtilityMethods.arraysSame(arr1, arr2));
   }
 
   @Test
   void matricesSameTest() {
-    int[][] matrix1 = new int[][] {{1,4,2,6},{5,8,6,7}};
-    int[][] matrix2 = new int[][] {{1,4,2,6},{5,8,6,7}};
+    var matrix1 = new int[][]{{1, 4, 2, 6}, {5, 8, 6, 7}};
+    var matrix2 = new int[][]{{1, 4, 2, 6}, {5, 8, 6, 7}};
     assertTrue(ArrayUtilityMethods.matricesSame(matrix1, matrix2));
   }
 

master-worker-pattern/src/test/java/com/iluwatar/masterworker/system/ArrayTransposeMasterWorkerTest.java

@@ -23,25 +23,38 @@
 
 package com.iluwatar.masterworker.system;
 
-import static org.junit.jupiter.api.Assertions.*;
-import org.junit.jupiter.api.Test;
-import com.iluwatar.masterworker.ArrayUtilityMethods;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import com.iluwatar.masterworker.ArrayInput;
 import com.iluwatar.masterworker.ArrayResult;
+import com.iluwatar.masterworker.ArrayUtilityMethods;
+import org.junit.jupiter.api.Test;
 
 /**
-* Testing getResult method in {@link ArrayTransposeMasterWorker} class.
-*/
+ * Testing getResult method in {@link ArrayTransposeMasterWorker} class.
+ */
 
 class ArrayTransposeMasterWorkerTest {
 
   @Test
   void getResultTest() {
-    ArrayTransposeMasterWorker atmw = new ArrayTransposeMasterWorker();
-    int[][] matrix = new int[][] {{1,2,3,4,5}, {1,2,3,4,5}, {1,2,3,4,5}, {1,2,3,4,5}, {1,2,3,4,5}};
-    int[][] matrixTranspose = new int[][] {{1,1,1,1,1}, {2,2,2,2,2}, {3,3,3,3,3}, {4,4,4,4,4}, {5,5,5,5,5}};
-    ArrayInput i = new ArrayInput(matrix);
-    ArrayResult r = (ArrayResult) atmw.getResult(i);
+    var atmw = new ArrayTransposeMasterWorker();
+    var matrix = new int[][]{
+        {1, 2, 3, 4, 5},
+        {1, 2, 3, 4, 5},
+        {1, 2, 3, 4, 5},
+        {1, 2, 3, 4, 5},
+        {1, 2, 3, 4, 5}
+    };
+    var matrixTranspose = new int[][]{
+        {1, 1, 1, 1, 1},
+        {2, 2, 2, 2, 2},
+        {3, 3, 3, 3, 3},
+        {4, 4, 4, 4, 4},
+        {5, 5, 5, 5, 5}
+    };
+    var i = new ArrayInput(matrix);
+    var r = (ArrayResult) atmw.getResult(i);
     assertTrue(ArrayUtilityMethods.matricesSame(r.data, matrixTranspose));
-  } 
+  }
 }

master-worker-pattern/src/test/java/com/iluwatar/masterworker/system/systemworkers/ArrayTransposeWorkerTest.java

@@ -23,29 +23,29 @@
 
 package com.iluwatar.masterworker.system.systemworkers;
 
-import static org.junit.jupiter.api.Assertions.*;
-import org.junit.jupiter.api.Test;
-import com.iluwatar.masterworker.ArrayUtilityMethods;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import com.iluwatar.masterworker.ArrayInput;
-import com.iluwatar.masterworker.ArrayResult;
+import com.iluwatar.masterworker.ArrayUtilityMethods;
 import com.iluwatar.masterworker.system.systemmaster.ArrayTransposeMaster;
+import org.junit.jupiter.api.Test;
 
 /**
-* Testing executeOperation method in {@link ArrayTransposeWorker} class.
-*/
+ * Testing executeOperation method in {@link ArrayTransposeWorker} class.
+ */
 
 class ArrayTransposeWorkerTest {
 
   @Test
   void executeOperationTest() {
-    ArrayTransposeMaster atm = new ArrayTransposeMaster(1);
-    ArrayTransposeWorker atw = new ArrayTransposeWorker(atm, 1);
-    int[][] matrix = new int[][] {{2,4}, {3,5}};
-    int[][] matrixTranspose = new int[][] {{2,3}, {4,5}};
-    ArrayInput i = new ArrayInput(matrix);
+    var atm = new ArrayTransposeMaster(1);
+    var atw = new ArrayTransposeWorker(atm, 1);
+    var matrix = new int[][]{{2, 4}, {3, 5}};
+    var matrixTranspose = new int[][]{{2, 3}, {4, 5}};
+    var i = new ArrayInput(matrix);
     atw.setReceivedData(atm, i);
-    ArrayResult r = atw.executeOperation();
+    var r = atw.executeOperation();
     assertTrue(ArrayUtilityMethods.matricesSame(r.data, matrixTranspose));
   }
-  
+
 }

mediator/src/main/java/com/iluwatar/mediator/Action.java

@@ -27,7 +27,6 @@ package com.iluwatar.mediator;
  * Action enumeration.
  */
 public enum Action {
-
   HUNT("hunted a rabbit", "arrives for dinner"),
   TALE("tells a tale", "comes to listen"),
   GOLD("found gold", "takes his share of the gold"),

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

@@ -55,10 +55,10 @@ public class App {
 
     // create party and members
     Party party = new PartyImpl();
-    Hobbit hobbit = new Hobbit();
-    Wizard wizard = new Wizard();
-    Rogue rogue = new Rogue();
-    Hunter hunter = new Hunter();
+    var hobbit = new Hobbit();
+    var wizard = new Wizard();
+    var rogue = new Rogue();
+    var hunter = new Hunter();
 
     // add party members
     party.addMember(hobbit);

mediator/src/main/java/com/iluwatar/mediator/PartyImpl.java

@@ -39,7 +39,7 @@ public class PartyImpl implements Party {
 
   @Override
   public void act(PartyMember actor, Action action) {
-    for (PartyMember member : members) {
+    for (var member : members) {
       if (!member.equals(actor)) {
         member.partyAction(action);
       }

mediator/src/test/java/com/iluwatar/mediator/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.mediator;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 }

mediator/src/test/java/com/iluwatar/mediator/PartyImplTest.java

@@ -43,10 +43,10 @@ public class PartyImplTest {
    */
   @Test
   public void testPartyAction() {
-    final PartyMember partyMember1 = mock(PartyMember.class);
-    final PartyMember partyMember2 = mock(PartyMember.class);
+    final var partyMember1 = mock(PartyMember.class);
+    final var partyMember2 = mock(PartyMember.class);
 
-    final PartyImpl party = new PartyImpl();
+    final var party = new PartyImpl();
     party.addMember(partyMember1);
     party.addMember(partyMember2);
 
@@ -58,7 +58,6 @@ public class PartyImplTest {
     verify(partyMember2).partyAction(Action.GOLD);
 
     verifyNoMoreInteractions(partyMember1, partyMember2);
-
   }
 
 }

mediator/src/test/java/com/iluwatar/mediator/PartyMemberTest.java

@@ -23,24 +23,24 @@
 
 package com.iluwatar.mediator;
 
-import ch.qos.logback.classic.Logger;
-import ch.qos.logback.classic.spi.ILoggingEvent;
-import ch.qos.logback.core.AppenderBase;
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.MethodSource;
-import org.slf4j.LoggerFactory;
-
-import java.util.Collection;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.function.Supplier;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.AppenderBase;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.slf4j.LoggerFactory;
+
 /**
  * Date: 12/19/15 - 10:13 PM
  *
@@ -48,12 +48,12 @@ import static org.mockito.Mockito.verify;
  */
 public class PartyMemberTest {
 
-  static Collection<Supplier<PartyMember>[]> dataProvider() {
-    return List.of(
-            new Supplier[]{Hobbit::new},
-            new Supplier[]{Hunter::new},
-            new Supplier[]{Rogue::new},
-            new Supplier[]{Wizard::new}
+  static Stream<Arguments> dataProvider() {
+    return Stream.of(
+        Arguments.of((Supplier<PartyMember>) Hobbit::new),
+        Arguments.of((Supplier<PartyMember>) Hunter::new),
+        Arguments.of((Supplier<PartyMember>) Rogue::new),
+        Arguments.of((Supplier<PartyMember>) Wizard::new)
     );
   }
 
@@ -75,9 +75,9 @@ public class PartyMemberTest {
   @ParameterizedTest
   @MethodSource("dataProvider")
   public void testPartyAction(Supplier<PartyMember> memberSupplier) {
-    final PartyMember member = memberSupplier.get();
+    final var member = memberSupplier.get();
 
-    for (final Action action : Action.values()) {
+    for (final var action : Action.values()) {
       member.partyAction(action);
       assertEquals(member.toString() + " " + action.getDescription(), appender.getLastMessage());
     }
@@ -91,16 +91,16 @@ public class PartyMemberTest {
   @ParameterizedTest
   @MethodSource("dataProvider")
   public void testAct(Supplier<PartyMember> memberSupplier) {
-    final PartyMember member = memberSupplier.get();
+    final var member = memberSupplier.get();
 
     member.act(Action.GOLD);
     assertEquals(0, appender.getLogSize());
 
-    final Party party = mock(Party.class);
+    final var party = mock(Party.class);
     member.joinedParty(party);
     assertEquals(member.toString() + " joins the party", appender.getLastMessage());
 
-    for (final Action action : Action.values()) {
+    for (final var action : Action.values()) {
       member.act(action);
       assertEquals(member.toString() + " " + action.toString(), appender.getLastMessage());
       verify(party).act(member, action);
@@ -114,16 +114,16 @@ public class PartyMemberTest {
    */
   @ParameterizedTest
   @MethodSource("dataProvider")
-  public void testToString(Supplier<PartyMember> memberSupplier) throws Exception {
-    final PartyMember member = memberSupplier.get();
-    final Class<? extends PartyMember> memberClass = member.getClass();
+  public void testToString(Supplier<PartyMember> memberSupplier) {
+    final var member = memberSupplier.get();
+    final var memberClass = member.getClass();
     assertEquals(memberClass.getSimpleName(), member.toString());
   }
 
-  private class InMemoryAppender extends AppenderBase<ILoggingEvent> {
+  private static class InMemoryAppender extends AppenderBase<ILoggingEvent> {
     private final List<ILoggingEvent> log = new LinkedList<>();
 
-    public InMemoryAppender(Class clazz) {
+    public InMemoryAppender(Class<?> clazz) {
       ((Logger) LoggerFactory.getLogger(clazz)).addAppender(this);
       start();
     }

memento/README.md

@@ -34,9 +34,12 @@ Let's first define the types of stars we are capable to handle.
 
 ```java
 public enum StarType {
-
-  SUN("sun"), RED_GIANT("red giant"), WHITE_DWARF("white dwarf"), SUPERNOVA("supernova"), DEAD(
-      "dead star"), UNDEFINED("");
+  SUN("sun"),
+  RED_GIANT("red giant"),
+  WHITE_DWARF("white dwarf"),
+  SUPERNOVA("supernova"),
+  DEAD("dead star"),
+  UNDEFINED("");
 
   private final String title;
 
@@ -95,8 +98,7 @@ public class Star {
   }
 
   StarMemento getMemento() {
-
-    StarMementoInternal state = new StarMementoInternal();
+    var state = new StarMementoInternal();
     state.setAgeYears(ageYears);
     state.setMassTons(massTons);
     state.setType(type);
@@ -104,8 +106,7 @@ public class Star {
   }
 
   void setMemento(StarMemento memento) {
-
-    StarMementoInternal state = (StarMementoInternal) memento;
+    var state = (StarMementoInternal) memento;
     this.type = state.getType();
     this.ageYears = state.getAgeYears();
     this.massTons = state.getMassTons();
@@ -152,8 +153,8 @@ public class Star {
 And finally here's how we use the mementos to store and restore star states.
 
 ```java
-    Stack<StarMemento> states = new Stack<>();
-    Star star = new Star(StarType.SUN, 10000000, 500000);
+    var states = new Stack<>();
+    var star = new Star(StarType.SUN, 10000000, 500000);
     LOGGER.info(star.toString());
     states.add(star.getMemento());
     star.timePasses();

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

@@ -52,9 +52,9 @@ public class App {
    * Program entry point.
    */
   public static void main(String[] args) {
-    Stack<StarMemento> states = new Stack<>();
+    var states = new Stack<StarMemento>();
 
-    Star star = new Star(StarType.SUN, 10000000, 500000);
+    var star = new Star(StarType.SUN, 10000000, 500000);
     LOGGER.info(star.toString());
     states.add(star.getMemento());
     star.timePasses();

memento/src/main/java/com/iluwatar/memento/Star.java

@@ -70,22 +70,18 @@ public class Star {
   }
 
   StarMemento getMemento() {
-
-    StarMementoInternal state = new StarMementoInternal();
+    var state = new StarMementoInternal();
     state.setAgeYears(ageYears);
     state.setMassTons(massTons);
     state.setType(type);
     return state;
-
   }
 
   void setMemento(StarMemento memento) {
-
-    StarMementoInternal state = (StarMementoInternal) memento;
+    var state = (StarMementoInternal) memento;
     this.type = state.getType();
     this.ageYears = state.getAgeYears();
     this.massTons = state.getMassTons();
-
   }
 
   @Override

memento/src/main/java/com/iluwatar/memento/StarType.java

@@ -27,9 +27,12 @@ package com.iluwatar.memento;
  * StarType enumeration.
  */
 public enum StarType {
-
-  SUN("sun"), RED_GIANT("red giant"), WHITE_DWARF("white dwarf"), SUPERNOVA("supernova"), DEAD(
-      "dead star"), UNDEFINED("");
+  SUN("sun"),
+  RED_GIANT("red giant"),
+  WHITE_DWARF("white dwarf"),
+  SUPERNOVA("supernova"),
+  DEAD("dead star"),
+  UNDEFINED("");
 
   private final String title;
 

memento/src/test/java/com/iluwatar/memento/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.memento;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 }

memento/src/test/java/com/iluwatar/memento/StarTest.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.memento;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/20/15 - 10:08 AM
  *
@@ -39,7 +39,7 @@ public class StarTest {
    */
   @Test
   public void testTimePasses() {
-    final Star star = new Star(StarType.SUN, 1, 2);
+    final var star = new Star(StarType.SUN, 1, 2);
     assertEquals("sun age: 1 years mass: 2 tons", star.toString());
 
     star.timePasses();
@@ -66,16 +66,16 @@ public class StarTest {
    */
   @Test
   public void testSetMemento() {
-    final Star star = new Star(StarType.SUN, 1, 2);
-    final StarMemento firstMemento = star.getMemento();
+    final var star = new Star(StarType.SUN, 1, 2);
+    final var firstMemento = star.getMemento();
     assertEquals("sun age: 1 years mass: 2 tons", star.toString());
 
     star.timePasses();
-    final StarMemento secondMemento = star.getMemento();
+    final var secondMemento = star.getMemento();
     assertEquals("red giant age: 2 years mass: 16 tons", star.toString());
 
     star.timePasses();
-    final StarMemento thirdMemento = star.getMemento();
+    final var thirdMemento = star.getMemento();
     assertEquals("white dwarf age: 4 years mass: 128 tons", star.toString());
 
     star.timePasses();

model-view-controller/src/main/java/com/iluwatar/model/view/controller/App.java

@@ -47,9 +47,9 @@ public class App {
    */
   public static void main(String[] args) {
     // create model, view and controller
-    GiantModel giant = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
-    GiantView view = new GiantView();
-    GiantController controller = new GiantController(giant, view);
+    var giant = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
+    var view = new GiantView();
+    var controller = new GiantController(giant, view);
     // initial display
     controller.updateView();
     // controller receives some interactions that affect the giant

model-view-controller/src/main/java/com/iluwatar/model/view/controller/Fatigue.java

@@ -27,8 +27,9 @@ package com.iluwatar.model.view.controller;
  * Fatigue enumeration.
  */
 public enum Fatigue {
-
-  ALERT("alert"), TIRED("tired"), SLEEPING("sleeping");
+  ALERT("alert"),
+  TIRED("tired"),
+  SLEEPING("sleeping");
 
   private final String title;
 

model-view-controller/src/main/java/com/iluwatar/model/view/controller/GiantController.java

@@ -36,6 +36,7 @@ public class GiantController {
     this.view = view;
   }
 
+  @SuppressWarnings("UnusedReturnValue")
   public Health getHealth() {
     return giant.getHealth();
   }
@@ -44,6 +45,7 @@ public class GiantController {
     this.giant.setHealth(health);
   }
 
+  @SuppressWarnings("UnusedReturnValue")
   public Fatigue getFatigue() {
     return giant.getFatigue();
   }
@@ -52,6 +54,7 @@ public class GiantController {
     this.giant.setFatigue(fatigue);
   }
 
+  @SuppressWarnings("UnusedReturnValue")
   public Nourishment getNourishment() {
     return giant.getNourishment();
   }

model-view-controller/src/main/java/com/iluwatar/model/view/controller/Health.java

@@ -27,8 +27,9 @@ package com.iluwatar.model.view.controller;
  * Health enumeration.
  */
 public enum Health {
-
-  HEALTHY("healthy"), WOUNDED("wounded"), DEAD("dead");
+  HEALTHY("healthy"),
+  WOUNDED("wounded"),
+  DEAD("dead");
 
   private final String title;
 

model-view-controller/src/main/java/com/iluwatar/model/view/controller/Nourishment.java

@@ -27,8 +27,9 @@ package com.iluwatar.model.view.controller;
  * Nourishment enumeration.
  */
 public enum Nourishment {
-
-  SATURATED("saturated"), HUNGRY("hungry"), STARVING("starving");
+  SATURATED("saturated"),
+  HUNGRY("hungry"),
+  STARVING("starving");
 
   private final String title;
 

model-view-controller/src/test/java/com/iluwatar/model/view/controller/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.model.view.controller;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 }

model-view-controller/src/test/java/com/iluwatar/model/view/controller/GiantControllerTest.java

@@ -23,13 +23,13 @@
 
 package com.iluwatar.model.view.controller;
 
-import org.junit.jupiter.api.Test;
-
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.verifyZeroInteractions;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/20/15 - 2:19 PM
  *
@@ -42,19 +42,20 @@ public class GiantControllerTest {
    */
   @Test
   public void testSetHealth() {
-    final GiantModel model = mock(GiantModel.class);
-    final GiantView view = mock(GiantView.class);
-    final GiantController controller = new GiantController(model, view);
+    final var model = mock(GiantModel.class);
+    final var view = mock(GiantView.class);
+    final var controller = new GiantController(model, view);
 
     verifyZeroInteractions(model, view);
 
-    for (final Health health : Health.values()) {
+    for (final var health : Health.values()) {
       controller.setHealth(health);
       verify(model).setHealth(health);
       verifyZeroInteractions(view);
     }
 
     controller.getHealth();
+    //noinspection ResultOfMethodCallIgnored
     verify(model).getHealth();
 
     verifyNoMoreInteractions(model, view);
@@ -65,19 +66,20 @@ public class GiantControllerTest {
    */
   @Test
   public void testSetFatigue() {
-    final GiantModel model = mock(GiantModel.class);
-    final GiantView view = mock(GiantView.class);
-    final GiantController controller = new GiantController(model, view);
+    final var model = mock(GiantModel.class);
+    final var view = mock(GiantView.class);
+    final var controller = new GiantController(model, view);
 
     verifyZeroInteractions(model, view);
 
-    for (final Fatigue fatigue : Fatigue.values()) {
+    for (final var fatigue : Fatigue.values()) {
       controller.setFatigue(fatigue);
       verify(model).setFatigue(fatigue);
       verifyZeroInteractions(view);
     }
 
     controller.getFatigue();
+    //noinspection ResultOfMethodCallIgnored
     verify(model).getFatigue();
 
     verifyNoMoreInteractions(model, view);
@@ -88,19 +90,20 @@ public class GiantControllerTest {
    */
   @Test
   public void testSetNourishment() {
-    final GiantModel model = mock(GiantModel.class);
-    final GiantView view = mock(GiantView.class);
-    final GiantController controller = new GiantController(model, view);
+    final var model = mock(GiantModel.class);
+    final var view = mock(GiantView.class);
+    final var controller = new GiantController(model, view);
 
     verifyZeroInteractions(model, view);
 
-    for (final Nourishment nourishment : Nourishment.values()) {
+    for (final var nourishment : Nourishment.values()) {
       controller.setNourishment(nourishment);
       verify(model).setNourishment(nourishment);
       verifyZeroInteractions(view);
     }
 
     controller.getNourishment();
+    //noinspection ResultOfMethodCallIgnored
     verify(model).getNourishment();
 
     verifyNoMoreInteractions(model, view);
@@ -108,9 +111,9 @@ public class GiantControllerTest {
 
   @Test
   public void testUpdateView() {
-    final GiantModel model = mock(GiantModel.class);
-    final GiantView view = mock(GiantView.class);
-    final GiantController controller = new GiantController(model, view);
+    final var model = mock(GiantModel.class);
+    final var view = mock(GiantView.class);
+    final var controller = new GiantController(model, view);
 
     verifyZeroInteractions(model, view);
 

model-view-controller/src/test/java/com/iluwatar/model/view/controller/GiantModelTest.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.model.view.controller;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/20/15 - 2:10 PM
  *
@@ -39,12 +39,13 @@ public class GiantModelTest {
    */
   @Test
   public void testSetHealth() {
-    final GiantModel model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
+    final var model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
     assertEquals(Health.HEALTHY, model.getHealth());
-    for (final Health health : Health.values()) {
+    var messageFormat = "The giant looks %s, alert and saturated.";
+    for (final var health : Health.values()) {
       model.setHealth(health);
       assertEquals(health, model.getHealth());
-      assertEquals("The giant looks " + health.toString() + ", alert and saturated.", model.toString());
+      assertEquals(String.format(messageFormat, health), model.toString());
     }
   }
 
@@ -53,12 +54,13 @@ public class GiantModelTest {
    */
   @Test
   public void testSetFatigue() {
-    final GiantModel model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
+    final var model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
     assertEquals(Fatigue.ALERT, model.getFatigue());
-    for (final Fatigue fatigue : Fatigue.values()) {
+    var messageFormat = "The giant looks healthy, %s and saturated.";
+    for (final var fatigue : Fatigue.values()) {
       model.setFatigue(fatigue);
       assertEquals(fatigue, model.getFatigue());
-      assertEquals("The giant looks healthy, " + fatigue.toString() + " and saturated.", model.toString());
+      assertEquals(String.format(messageFormat, fatigue), model.toString());
     }
   }
 
@@ -67,12 +69,13 @@ public class GiantModelTest {
    */
   @Test
   public void testSetNourishment() {
-    final GiantModel model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
+    final var model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
     assertEquals(Nourishment.SATURATED, model.getNourishment());
-    for (final Nourishment nourishment : Nourishment.values()) {
+    var messageFormat = "The giant looks healthy, alert and %s.";
+    for (final var nourishment : Nourishment.values()) {
       model.setNourishment(nourishment);
       assertEquals(nourishment, model.getNourishment());
-      assertEquals("The giant looks healthy, alert and " + nourishment.toString() + ".", model.toString());
+      assertEquals(String.format(messageFormat, nourishment), model.toString());
     }
   }
 

model-view-controller/src/test/java/com/iluwatar/model/view/controller/GiantViewTest.java

@@ -31,7 +31,6 @@ import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.AppenderBase;
 import java.util.LinkedList;
 import java.util.List;
-
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -62,9 +61,9 @@ public class GiantViewTest {
    */
   @Test
   public void testDisplayGiant() {
-    final GiantView view = new GiantView();
+    final var view = new GiantView();
 
-    final GiantModel model = mock(GiantModel.class);
+    final var model = mock(GiantModel.class);
     view.displayGiant(model);
 
     assertEquals(model.toString(), appender.getLastMessage());
@@ -74,10 +73,10 @@ public class GiantViewTest {
   /**
    * Logging Appender Implementation
    */
-  public class InMemoryAppender extends AppenderBase<ILoggingEvent> {
+  public static class InMemoryAppender extends AppenderBase<ILoggingEvent> {
     private final List<ILoggingEvent> log = new LinkedList<>();
 
-    public InMemoryAppender(Class clazz) {
+    public InMemoryAppender(Class<?> clazz) {
       ((Logger) LoggerFactory.getLogger(clazz)).addAppender(this);
       start();
     }

model-view-presenter/src/main/java/com/iluwatar/model/view/presenter/App.java

@@ -44,9 +44,9 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    FileLoader loader = new FileLoader();
-    FileSelectorJFrame frame = new FileSelectorJFrame();
-    FileSelectorPresenter presenter = new FileSelectorPresenter(frame);
+    var loader = new FileLoader();
+    var frame = new FileSelectorJFrame();
+    var presenter = new FileSelectorPresenter(frame);
     presenter.setLoader(loader);
     presenter.start();
   }

model-view-presenter/src/main/java/com/iluwatar/model/view/presenter/FileLoader.java

@@ -27,6 +27,7 @@ import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileReader;
 import java.io.Serializable;
+import java.util.stream.Collectors;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -59,18 +60,11 @@ public class FileLoader implements Serializable {
    * Loads the data of the file specified.
    */
   public String loadData() {
-    String dataFileName = this.fileName;
-    try (BufferedReader br = new BufferedReader(new FileReader(new File(dataFileName)))) {
-      StringBuilder sb = new StringBuilder();
-      String line;
-
-      while ((line = br.readLine()) != null) {
-        sb.append(line).append('\n');
-      }
-
+    var dataFileName = this.fileName;
+    try (var br = new BufferedReader(new FileReader(new File(dataFileName)))) {
+      var result = br.lines().collect(Collectors.joining("\n"));
       this.loaded = true;
-
-      return sb.toString();
+      return result;
     } catch (Exception e) {
       LOGGER.error("File {} does not exist", dataFileName);
     }

model-view-presenter/src/main/java/com/iluwatar/model/view/presenter/FileSelectorJFrame.java

@@ -55,16 +55,6 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
    */
   private final JButton cancel;
 
-  /**
-   * The information label.
-   */
-  private final JLabel info;
-
-  /**
-   * The contents label.
-   */
-  private final JLabel contents;
-
   /**
    * The text field for giving the name of the file that we want to open.
    */
@@ -75,11 +65,6 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
    */
   private final JTextArea area;
 
-  /**
-   * The panel that will hold our widgets.
-   */
-  private final JPanel panel;
-
   /**
    * The Presenter component that the frame will interact with.
    */
@@ -102,7 +87,7 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
     /*
      * Add the panel.
      */
-    this.panel = new JPanel();
+    var panel = new JPanel();
     panel.setLayout(null);
     this.add(panel);
     panel.setBounds(0, 0, 500, 200);
@@ -111,32 +96,32 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
     /*
      * Add the info label.
      */
-    this.info = new JLabel("File Name :");
-    this.panel.add(info);
+    var info = new JLabel("File Name :");
+    panel.add(info);
     info.setBounds(30, 10, 100, 30);
 
     /*
      * Add the contents label.
      */
-    this.contents = new JLabel("File contents :");
-    this.panel.add(contents);
-    this.contents.setBounds(30, 100, 120, 30);
+    var contents = new JLabel("File contents :");
+    panel.add(contents);
+    contents.setBounds(30, 100, 120, 30);
 
     /*
      * Add the text field.
      */
     this.input = new JTextField(100);
-    this.panel.add(input);
+    panel.add(input);
     this.input.setBounds(150, 15, 200, 20);
 
     /*
      * Add the text area.
      */
     this.area = new JTextArea(100, 100);
-    JScrollPane pane = new JScrollPane(area);
+    var pane = new JScrollPane(area);
     pane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
     pane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
-    this.panel.add(pane);
+    panel.add(pane);
     this.area.setEditable(false);
     pane.setBounds(150, 100, 250, 80);
 
@@ -144,7 +129,7 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
      * Add the OK button.
      */
     this.ok = new JButton("OK");
-    this.panel.add(ok);
+    panel.add(ok);
     this.ok.setBounds(250, 50, 100, 25);
     this.ok.addActionListener(this);
 
@@ -152,7 +137,7 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
      * Add the cancel button.
      */
     this.cancel = new JButton("Cancel");
-    this.panel.add(this.cancel);
+    panel.add(this.cancel);
     this.cancel.setBounds(380, 50, 100, 25);
     this.cancel.addActionListener(this);
 

model-view-presenter/src/main/java/com/iluwatar/model/view/presenter/FileSelectorPresenter.java

@@ -91,7 +91,7 @@ public class FileSelectorPresenter implements Serializable {
     }
 
     if (loader.fileExists()) {
-      String data = loader.loadData();
+      var data = loader.loadData();
       view.displayData(data);
     } else {
       view.showMessage("The file specified does not exist.");

model-view-presenter/src/test/java/com/iluwatar/model/view/presenter/AppTest.java

@@ -26,16 +26,13 @@ package com.iluwatar.model.view.presenter;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 
 }

model-view-presenter/src/test/java/com/iluwatar/model/view/presenter/FileLoaderTest.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.model.view.presenter;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertNull;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/21/15 - 12:12 PM
  *
@@ -35,8 +35,8 @@ import static org.junit.jupiter.api.Assertions.assertNull;
 public class FileLoaderTest {
 
   @Test
-  public void testLoadData() throws Exception {
-    final FileLoader fileLoader = new FileLoader();
+  public void testLoadData() {
+    final var fileLoader = new FileLoader();
     fileLoader.setFileName("non-existing-file");
     assertNull(fileLoader.loadData());
   }

model-view-presenter/src/test/java/com/iluwatar/model/view/presenter/FileSelectorPresenterTest.java

@@ -23,14 +23,14 @@
 
 package com.iluwatar.model.view.presenter;
 
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
 /**
  * This test case is responsible for testing our application by taking advantage of the
  * Model-View-Controller architectural pattern.
@@ -79,7 +79,7 @@ public class FileSelectorPresenterTest {
    */
   @Test
   public void updateFileNameToLoader() {
-    String expectedFile = "Stamatis";
+    var expectedFile = "Stamatis";
     stub.setFileName(expectedFile);
 
     presenter.start();

module/pom.xml

@@ -23,38 +23,39 @@
     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>module</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.module.App</mainClass>
-								</manifest>
-							</archive>
-						</configuration>
-					</execution>
-				</executions>
-			</plugin>
-		</plugins>
-	</build>
+<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>module</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.module.App</mainClass>
+                                </manifest>
+                            </archive>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
 </project>

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

@@ -67,10 +67,8 @@ public class App {
 
   /**
    * Following method is main executor.
-   *
-   * @param args for providing default program arguments
    */
-  public static void execute(final String... args) {
+  public static void execute() {
 
     /* Send logs on file system */
     fileLoggerModule.printString(MESSAGE);
@@ -90,7 +88,7 @@ public class App {
    */
   public static void main(final String... args) throws FileNotFoundException {
     prepare();
-    execute(args);
+    execute();
     unprepare();
   }
 }