Achieved milestone 1.9.0

Add unit tests for remaining patterns

CODE_COVERAGE.md

@@ -0,0 +1,13 @@
+# Code Coverage Report generation
+
+To generate the code coverage report, execute the following command:
+> mvn clean verify
+
+This will generate code coverage report in each of the modules. In order to view the same, open the following file in your browser.
+> target/site/jacoco/index.html 
+
+Please note that the above folder is created under each of the modules. For example:
+* adapter/target/site/jacoco/index.html 
+* busniess-delegate/target/site/jacoco/index.html 
+
+

CONTRIBUTING.MD

@@ -0,0 +1,4 @@
+This is great you have something to contribute! 
+
+Before going any further please read the [wiki](https://github.com/iluwatar/java-design-patterns/wiki)
+with conventions and rules we used for this project.

README.md

@@ -2,11 +2,10 @@
      that smart and dearly wants an empty line before a heading to be able to
      display it as such, e.g. website) -->
 
-# Design pattern samples in Java
+# Design patterns implemented in Java
 
 [![Build status](https://travis-ci.org/iluwatar/java-design-patterns.svg?branch=master)](https://travis-ci.org/iluwatar/java-design-patterns)
 [![Coverage Status](https://coveralls.io/repos/iluwatar/java-design-patterns/badge.svg?branch=master)](https://coveralls.io/r/iluwatar/java-design-patterns?branch=master)
-[![Coverity Scan Build Status](https://scan.coverity.com/projects/5634/badge.svg)](https://scan.coverity.com/projects/5634)
 [![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)
 
 # Introduction
@@ -40,7 +39,7 @@ patterns by any of the following approaches
 
 # How to contribute
 
-If you are willing to contribute to the project you will find the relevant information in our [developer wiki](https://github.com/iluwatar/java-design-patterns/wiki).
+If you are willing to contribute to the project you will find the relevant information in our [developer wiki](https://github.com/iluwatar/java-design-patterns/wiki). We will help you and answer your questions in the [Gitter chatroom](https://gitter.im/iluwatar/java-design-patterns).
 
 # Credits
 

abstract-factory/index.md

@@ -7,8 +7,11 @@ categories: Creational
 tags: 
  - Java
  - Gang Of Four
+ - Difficulty-Intermediate
 ---
 
+**Also known as:** Kit
+
 **Intent:** Provide an interface for creating families of related or dependent
 objects without specifying their concrete classes.
 

abstract-factory/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.7.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>abstract-factory</artifactId>
   <dependencies>

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

@@ -1,82 +1,105 @@
 package com.iluwatar.abstractfactory;
 
-
 /**
  * 
- * The Abstract Factory pattern provides a way to encapsulate a group of individual 
- * factories that have a common theme without specifying their concrete classes. In 
- * normal usage, the client software creates a concrete implementation of the abstract 
- * factory and then uses the generic interface of the factory to create the concrete 
- * objects that are part of the theme. The client does not know (or care) which 
- * concrete objects it gets from each of these internal factories, since it uses only 
- * the generic interfaces of their products. This pattern separates the details of 
- * implementation of a set of objects from their general usage and relies on object 
- * composition, as object creation is implemented in methods exposed in the factory 
- * interface.
+ * The Abstract Factory pattern provides a way to encapsulate a group of individual factories that have a common theme
+ * without specifying their concrete classes. In normal usage, the client software creates a concrete implementation of
+ * the abstract factory and then uses the generic interface of the factory to create the concrete objects that are part
+ * of the theme. The client does not know (or care) which concrete objects it gets from each of these internal
+ * factories, since it uses only the generic interfaces of their products. This pattern separates the details of
+ * implementation of a set of objects from their general usage and relies on object composition, as object creation is
+ * implemented in methods exposed in the factory interface.
  * <p>
- * The essence of the Abstract Factory pattern is a factory interface
- * ({@link KingdomFactory}) and its implementations ({@link ElfKingdomFactory},
- * {@link OrcKingdomFactory}). The example uses both concrete implementations to 
- * create a king, a castle and an army.
+ * The essence of the Abstract Factory pattern is a factory interface ({@link KingdomFactory}) and its implementations (
+ * {@link ElfKingdomFactory}, {@link OrcKingdomFactory}). The example uses both concrete implementations to create a
+ * king, a castle and an army.
  * 
  */
 public class App {
 
-	private King king;
-	private Castle castle;
-	private Army army;
+  private King king;
+  private Castle castle;
+  private Army army;
+
+  /**
+   * Creates kingdom
+   */
+  public void createKingdom(final KingdomFactory factory) {
+    setKing(factory.createKing());
+    setCastle(factory.createCastle());
+    setArmy(factory.createArmy());
+  }
+
+  ElfKingdomFactory getElfKingdomFactory() {
+    return new ElfKingdomFactory();
+  }
+
+  OrcKingdomFactory getOrcKingdomFactory() {
+    return new OrcKingdomFactory();
+  }
+
+  King getKing(final KingdomFactory factory) {
+    return factory.createKing();
+  }
+
+  public King getKing() {
+    return king;
+  }
+
+  private void setKing(final King king) {
+    this.king = king;
+  }
+  
+  Castle getCastle(final KingdomFactory factory) {
+    return factory.createCastle();
+  }
+
+  public Castle getCastle() {
+    return castle;
+  }
+
+  private void setCastle(final Castle castle) {
+    this.castle = castle;
+  }
+  
+  Army getArmy(final KingdomFactory factory) {
+    return factory.createArmy();
+  }
+
+  public Army getArmy() {
+    return army;
+  }
+
+  private void setArmy(final Army army) {
+    this.army = army;
+  }
+  
+  /**
+   * Program entry point
+   * 
+   * @param args
+   *          command line args
+   */
+  public static void main(String[] args) {
+
+    App app = new App();
+
+    System.out.println("Elf Kingdom");
+    KingdomFactory elfKingdomFactory;
+    elfKingdomFactory = app.getElfKingdomFactory();
+    app.createKingdom(elfKingdomFactory);
+    System.out.println(app.getArmy().getDescription());
+    System.out.println(app.getCastle().getDescription());
+    System.out.println(app.getKing().getDescription());
+
+    System.out.println("\nOrc Kingdom");
+    KingdomFactory orcKingdomFactory;
+    orcKingdomFactory = app.getOrcKingdomFactory();
+    app.createKingdom(orcKingdomFactory);
+    System.out.println(app.getArmy().getDescription());
+    System.out.println(app.getCastle().getDescription());
+    System.out.println(app.getKing().getDescription());
+
+  }
 
-	/**
-	 * Creates kingdom
-	 * @param factory
-	 */
-	public void createKingdom(final KingdomFactory factory) {
-		setKing(factory.createKing());
-		setCastle(factory.createCastle());
-		setArmy(factory.createArmy());
-	}
-	
-	ElfKingdomFactory getElfKingdomFactory() {
-		return new ElfKingdomFactory();
-	}
-	
-	OrcKingdomFactory getOrcKingdomFactory() {
-		return new OrcKingdomFactory();
-	}
-	
-	King getKing(final KingdomFactory factory) {
-		return factory.createKing();
-	}
-	
-	Castle getCastle(final KingdomFactory factory) {
-		return factory.createCastle();
-	}
-	
-	Army getArmy(final KingdomFactory factory) {
-		return factory.createArmy();
-	}
-	
-	public King getKing() {
-		return king;
-	}
-	
-	private void setKing(final King king) {
-		this.king = king;
-	}
-	
-	public Castle getCastle() {
-		return castle;
-	}
-	
-	private void setCastle(final Castle castle) {
-		this.castle = castle;
-	}
-	
-	public Army getArmy() {
-		return army;
-	}
-	
-	private void setArmy(final Army army) {
-		this.army = army;
-	}
 }

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

@@ -7,5 +7,5 @@ package com.iluwatar.abstractfactory;
  */
 public interface Army {
 
-	String getDescription();
+  String getDescription();
 }

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

@@ -7,5 +7,5 @@ package com.iluwatar.abstractfactory;
  */
 public interface Castle {
 
-	String getDescription();
+  String getDescription();
 }

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

@@ -7,10 +7,10 @@ package com.iluwatar.abstractfactory;
  */
 public class ElfArmy implements Army {
 
-	static final String DESCRIPTION = "This is the Elven Army!";
+  static final String DESCRIPTION = "This is the Elven Army!";
 
-	@Override
-	public String getDescription() {
-		return DESCRIPTION;
-	}
+  @Override
+  public String getDescription() {
+    return DESCRIPTION;
+  }
 }

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

@@ -7,10 +7,10 @@ package com.iluwatar.abstractfactory;
  */
 public class ElfCastle implements Castle {
 
-	static final String DESCRIPTION = "This is the Elven castle!";
+  static final String DESCRIPTION = "This is the Elven castle!";
 
-	@Override
-	public String getDescription() {
-		return DESCRIPTION;
-	}
+  @Override
+  public String getDescription() {
+    return DESCRIPTION;
+  }
 }

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

@@ -7,10 +7,10 @@ package com.iluwatar.abstractfactory;
  */
 public class ElfKing implements King {
 
-	static final String DESCRIPTION = "This is the Elven king!";
-	
-	@Override
-	public String getDescription() {
-		return DESCRIPTION;
-	}
+  static final String DESCRIPTION = "This is the Elven king!";
+
+  @Override
+  public String getDescription() {
+    return DESCRIPTION;
+  }
 }

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

@@ -7,16 +7,16 @@ package com.iluwatar.abstractfactory;
  */
 public class ElfKingdomFactory implements KingdomFactory {
 
-	public Castle createCastle() {
-		return new ElfCastle();
-	}
+  public Castle createCastle() {
+    return new ElfCastle();
+  }
 
-	public King createKing() {
-		return new ElfKing();
-	}
+  public King createKing() {
+    return new ElfKing();
+  }
 
-	public Army createArmy() {
-		return new ElfArmy();
-	}
+  public Army createArmy() {
+    return new ElfArmy();
+  }
 
 }

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

@@ -7,5 +7,5 @@ package com.iluwatar.abstractfactory;
  */
 public interface King {
 
-	String getDescription();
+  String getDescription();
 }

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

@@ -7,10 +7,10 @@ package com.iluwatar.abstractfactory;
  */
 public interface KingdomFactory {
 
-	Castle createCastle();
+  Castle createCastle();
 
-	King createKing();
+  King createKing();
 
-	Army createArmy();
+  Army createArmy();
 
 }

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

@@ -7,10 +7,10 @@ package com.iluwatar.abstractfactory;
  */
 public class OrcArmy implements Army {
 
-	static final String DESCRIPTION = "This is the Orc Army!";
+  static final String DESCRIPTION = "This is the Orc Army!";
 
-	@Override
-	public String getDescription() {
-		return DESCRIPTION;
-	}
+  @Override
+  public String getDescription() {
+    return DESCRIPTION;
+  }
 }

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

@@ -7,10 +7,10 @@ package com.iluwatar.abstractfactory;
  */
 public class OrcCastle implements Castle {
 
-	static final String DESCRIPTION = "This is the Orc castle!";
+  static final String DESCRIPTION = "This is the Orc castle!";
 
-	@Override
-	public String getDescription() {
-		return DESCRIPTION;
-	}
+  @Override
+  public String getDescription() {
+    return DESCRIPTION;
+  }
 }

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

@@ -7,10 +7,10 @@ package com.iluwatar.abstractfactory;
  */
 public class OrcKing implements King {
 
-static final String DESCRIPTION = "This is the Orc king!";
-	
-	@Override
-	public String getDescription() {
-		return DESCRIPTION;
-	}
+  static final String DESCRIPTION = "This is the Orc king!";
+
+  @Override
+  public String getDescription() {
+    return DESCRIPTION;
+  }
 }

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

@@ -7,16 +7,15 @@ package com.iluwatar.abstractfactory;
  */
 public class OrcKingdomFactory implements KingdomFactory {
 
-	public Castle createCastle() {
-		return new OrcCastle();
-	}
+  public Castle createCastle() {
+    return new OrcCastle();
+  }
 
-	public King createKing() {
-		return new OrcKing();
-	}
-
-	public Army createArmy() {
-		return new OrcArmy();
-	}
+  public King createKing() {
+    return new OrcKing();
+  }
 
+  public Army createArmy() {
+    return new OrcArmy();
+  }
 }

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

@@ -1,4 +1,5 @@
 package com.iluwatar.abstractfactory;
+
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
@@ -7,71 +8,71 @@ import org.junit.Test;
 
 public class AppTest {
 
-	private App app = new App();
-	private KingdomFactory elfFactory;
-	private KingdomFactory orcFactory;
-	
-	@Before
-	public void setUp() {
-		elfFactory = app.getElfKingdomFactory();
-		orcFactory = app.getOrcKingdomFactory();
-	}
-	
-	@Test
-	public void king() {
-		final King elfKing = app.getKing(elfFactory);
-		assertTrue(elfKing instanceof ElfKing);
-		assertEquals(ElfKing.DESCRIPTION, elfKing.getDescription());
-		final King orcKing = app.getKing(orcFactory);
-		assertTrue(orcKing instanceof OrcKing);
-		assertEquals(OrcKing.DESCRIPTION, orcKing.getDescription());
-	}
-	
-	@Test
-	public void castle() {
-		final Castle elfCastle = app.getCastle(elfFactory);
-		assertTrue(elfCastle instanceof ElfCastle);
-		assertEquals(ElfCastle.DESCRIPTION, elfCastle.getDescription());
-		final Castle orcCastle = app.getCastle(orcFactory);
-		assertTrue(orcCastle instanceof OrcCastle);
-		assertEquals(OrcCastle.DESCRIPTION, orcCastle.getDescription());
-	}
-	
-	@Test
-	public void army() {
-		final Army elfArmy = app.getArmy(elfFactory);
-		assertTrue(elfArmy instanceof ElfArmy);
-		assertEquals(ElfArmy.DESCRIPTION, elfArmy.getDescription());
-		final Army orcArmy = app.getArmy(orcFactory);
-		assertTrue(orcArmy instanceof OrcArmy);
-		assertEquals(OrcArmy.DESCRIPTION, orcArmy.getDescription());
-	}
-	
-	@Test
-	public void createElfKingdom() {
-		app.createKingdom(elfFactory);
-		final King king = app.getKing();
-		final Castle castle = app.getCastle();
-		final Army army = app.getArmy();
-		assertTrue(king instanceof ElfKing);
-		assertEquals(ElfKing.DESCRIPTION, king.getDescription());
-		assertTrue(castle instanceof ElfCastle);
-		assertEquals(ElfCastle.DESCRIPTION, castle.getDescription());
-		assertTrue(army instanceof ElfArmy);
-		assertEquals(ElfArmy.DESCRIPTION, army.getDescription());
-	}
-	
-	@Test
-	public void createOrcKingdom() {
-		app.createKingdom(orcFactory);
-		final King king = app.getKing();
-		final Castle castle = app.getCastle();
-		final Army army = app.getArmy();
-		assertTrue(king instanceof OrcKing);
-		assertEquals(OrcKing.DESCRIPTION, king.getDescription());
-		assertTrue(castle instanceof OrcCastle);
-		assertEquals(OrcCastle.DESCRIPTION, castle.getDescription());
-		assertTrue(army instanceof OrcArmy);
-		assertEquals(OrcArmy.DESCRIPTION, army.getDescription());
-	}
+  private App app = new App();
+  private KingdomFactory elfFactory;
+  private KingdomFactory orcFactory;
+
+  @Before
+  public void setUp() {
+    elfFactory = app.getElfKingdomFactory();
+    orcFactory = app.getOrcKingdomFactory();
+  }
+
+  @Test
+  public void king() {
+    final King elfKing = app.getKing(elfFactory);
+    assertTrue(elfKing instanceof ElfKing);
+    assertEquals(ElfKing.DESCRIPTION, elfKing.getDescription());
+    final King orcKing = app.getKing(orcFactory);
+    assertTrue(orcKing instanceof OrcKing);
+    assertEquals(OrcKing.DESCRIPTION, orcKing.getDescription());
+  }
+
+  @Test
+  public void castle() {
+    final Castle elfCastle = app.getCastle(elfFactory);
+    assertTrue(elfCastle instanceof ElfCastle);
+    assertEquals(ElfCastle.DESCRIPTION, elfCastle.getDescription());
+    final Castle orcCastle = app.getCastle(orcFactory);
+    assertTrue(orcCastle instanceof OrcCastle);
+    assertEquals(OrcCastle.DESCRIPTION, orcCastle.getDescription());
+  }
+
+  @Test
+  public void army() {
+    final Army elfArmy = app.getArmy(elfFactory);
+    assertTrue(elfArmy instanceof ElfArmy);
+    assertEquals(ElfArmy.DESCRIPTION, elfArmy.getDescription());
+    final Army orcArmy = app.getArmy(orcFactory);
+    assertTrue(orcArmy instanceof OrcArmy);
+    assertEquals(OrcArmy.DESCRIPTION, orcArmy.getDescription());
+  }
+
+  @Test
+  public void createElfKingdom() {
+    app.createKingdom(elfFactory);
+    final King king = app.getKing();
+    final Castle castle = app.getCastle();
+    final Army army = app.getArmy();
+    assertTrue(king instanceof ElfKing);
+    assertEquals(ElfKing.DESCRIPTION, king.getDescription());
+    assertTrue(castle instanceof ElfCastle);
+    assertEquals(ElfCastle.DESCRIPTION, castle.getDescription());
+    assertTrue(army instanceof ElfArmy);
+    assertEquals(ElfArmy.DESCRIPTION, army.getDescription());
+  }
+
+  @Test
+  public void createOrcKingdom() {
+    app.createKingdom(orcFactory);
+    final King king = app.getKing();
+    final Castle castle = app.getCastle();
+    final Army army = app.getArmy();
+    assertTrue(king instanceof OrcKing);
+    assertEquals(OrcKing.DESCRIPTION, king.getDescription());
+    assertTrue(castle instanceof OrcCastle);
+    assertEquals(OrcCastle.DESCRIPTION, castle.getDescription());
+    assertTrue(army instanceof OrcArmy);
+    assertEquals(OrcArmy.DESCRIPTION, army.getDescription());
+  }
 }

adapter/etc/adapter.ucls

@@ -1,61 +1,61 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true" 
-  realizations="true" associations="true" dependencies="false" nesting-relationships="true">  
-  <class id="1" language="java" name="com.iluwatar.adapter.GnomeEngineeringManager" project="adapter" 
-    file="/adapter/src/main/java/com/iluwatar/adapter/GnomeEngineeringManager.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="106" width="224" x="110" y="210"/>    
+<class-diagram version="1.1.9" icons="true" always-add-relationships="false" generalizations="true" realizations="true" 
+  associations="true" dependencies="false" nesting-relationships="true" router="FAN">  
+  <class id="1" language="java" name="com.iluwatar.adapter.FishingBoat" project="adapter" 
+    file="/adapter/src/main/java/com/iluwatar/adapter/FishingBoat.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="656" y="355"/>    
     <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="2" language="java" name="com.iluwatar.adapter.Engineer" project="adapter" 
-    file="/adapter/src/main/java/com/iluwatar/adapter/Engineer.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="88" width="141" x="110" y="356"/>    
+  <class id="2" language="java" name="com.iluwatar.adapter.Captain" project="adapter" 
+    file="/adapter/src/main/java/com/iluwatar/adapter/Captain.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="228" y="185"/>    
+    <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.adapter.BattleFishingBoat" project="adapter" 
+    file="/adapter/src/main/java/com/iluwatar/adapter/BattleFishingBoat.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="463" y="357"/>    
+    <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="4" language="java" name="com.iluwatar.adapter.BattleShip" project="adapter" 
+    file="/adapter/src/main/java/com/iluwatar/adapter/BattleShip.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="466" y="170"/>    
     <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="3" language="java" name="com.iluwatar.adapter.GnomeEngineer" project="adapter" 
-    file="/adapter/src/main/java/com/iluwatar/adapter/GnomeEngineer.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="106" width="141" x="374" y="210"/>    
-    <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.adapter.GoblinGlider" project="adapter" 
-    file="/adapter/src/main/java/com/iluwatar/adapter/GoblinGlider.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="142" width="130" x="374" y="356"/>    
-    <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>  
   <realization id="5">    
-    <end type="SOURCE" refId="1"/>    
-    <end type="TARGET" refId="2"/>  
+    <end type="SOURCE" refId="2"/>    
+    <end type="TARGET" refId="4"/>  
   </realization>  
-  <realization id="6">    
-    <end type="SOURCE" refId="3"/>    
-    <end type="TARGET" refId="2"/>  
-  </realization>  
-  <association id="7">    
-    <end type="SOURCE" refId="1" navigable="false">      
-      <attribute id="8" name="engineer"/>      
-      <multiplicity id="9" minimum="0" maximum="1"/>    
+  <association id="6">    
+    <end type="SOURCE" refId="3" navigable="false">      
+      <attribute id="7" name="boat"/>      
+      <multiplicity id="8" minimum="0" maximum="1"/>    
     </end>    
-    <end type="TARGET" refId="2" navigable="true"/>    
+    <end type="TARGET" refId="1" navigable="true"/>    
     <display labels="true" multiplicity="true"/>  
   </association>  
+  <realization id="9">    
+    <end type="SOURCE" refId="3"/>    
+    <end type="TARGET" refId="4"/>  
+  </realization>  
   <association id="10">    
-    <end type="SOURCE" refId="3" navigable="false">      
-      <attribute id="11" name="glider"/>      
+    <end type="SOURCE" refId="2" navigable="false">      
+      <attribute id="11" name="battleship"/>      
       <multiplicity id="12" minimum="0" maximum="1"/>    
     </end>    
     <end type="TARGET" refId="4" navigable="true"/>    

adapter/index.md

@@ -7,13 +7,16 @@ categories: Structural
 tags:
  - Java
  - Gang Of Four
+ - Difficulty-Beginner
 ---
 
+**Also known as:** 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.
 
-![alt text](./etc/adapter_1.png "Adapter")
+![alt text](./etc/adapter.png "Adapter")
 
 **Applicability:** Use the Adapter pattern when
 

adapter/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.7.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>adapter</artifactId>
   <dependencies>
@@ -14,5 +14,10 @@
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

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

@@ -1,31 +1,38 @@
 package com.iluwatar.adapter;
 
 /**
+ * An adapter helps two incompatible interfaces to work together. This is the real world definition
+ * for an adapter. Interfaces may be incompatible but the inner functionality should suit the need.
+ * The Adapter design pattern allows otherwise incompatible classes to work together by converting
+ * the interface of one class into an interface expected by the clients.
  *
- * An adapter helps two incompatible interfaces to work together. This is the real 
- * world definition for an adapter. Interfaces may be incompatible but the inner 
- * functionality should suit the need. The Adapter design pattern allows otherwise 
- * incompatible classes to work together by converting the interface of one class 
- * into an interface expected by the clients.
  * <p>
- * There are two variations of the Adapter pattern: The class adapter implements
- * the adaptee's interface whereas the object adapter uses composition to
- * contain the adaptee in the adapter object. This example uses the object
- * adapter approach.
+ * There are two variations of the Adapter pattern: The class adapter implements the adaptee's
+ * interface whereas the object adapter uses composition to contain the adaptee in the adapter
+ * object. This example uses the object adapter approach.
+ *
  * <p>
- * The Adapter ({@link GnomeEngineer}) converts the interface of the target class
- * ({@link GoblinGlider}) into a suitable one expected by the client
- * ({@link GnomeEngineeringManager}).
- * 
+ * The Adapter ({@link BattleFishingBoat}) converts the interface of the adaptee class (
+ * {@link FishingBoat}) into a suitable one expected by the client ( {@link BattleShip} ).
+ *
+ * <p>
+ * The story of this implementation is this. <br>
+ * Pirates are coming! we need a {@link BattleShip} to fight! We have a {@link FishingBoat} and our
+ * captain. We have no time to make up a new ship! we need to reuse this {@link FishingBoat}. The
+ * captain needs a battleship which can fire and move. The spec is in {@link BattleShip}. We will
+ * use the Adapter pattern to reuse {@link FishingBoat}.
+ *
  */
 public class App {
 
-	/**
-	 * Program entry point
-	 * @param args command line args
-	 */
-	public static void main(String[] args) {
-		Engineer manager = new GnomeEngineeringManager();
-		manager.operateDevice();
-	}
+  /**
+   * Program entry point.
+   *
+   * @param args command line args
+   */
+  public static void main(String[] args) {
+    Captain captain = new Captain(new BattleFishingBoat());
+    captain.move();
+    captain.fire();
+  }
 }

adapter/src/main/java/com/iluwatar/adapter/BattleFishingBoat.java

@@ -0,0 +1,29 @@
+package com.iluwatar.adapter;
+
+/**
+ *
+ * Adapter class. Adapts the interface of the device ({@link FishingBoat}) into {@link BattleShip}
+ * interface expected by the client ({@link Captain}). <br>
+ * In this case we added a new function fire to suit the interface. We are reusing the
+ * {@link FishingBoat} without changing itself. The Adapter class can just map the functions of the
+ * Adaptee or add, delete features of the Adaptee.
+ *
+ */
+public class BattleFishingBoat implements BattleShip {
+
+  private FishingBoat boat;
+
+  public BattleFishingBoat() {
+    boat = new FishingBoat();
+  }
+
+  @Override
+  public void fire() {
+    System.out.println("fire!");
+  }
+
+  @Override
+  public void move() {
+    boat.sail();
+  }
+}

adapter/src/main/java/com/iluwatar/adapter/BattleShip.java

@@ -0,0 +1,14 @@
+package com.iluwatar.adapter;
+
+/**
+ * The interface expected by the client.<br>
+ * A Battleship can fire and move.
+ *
+ */
+public interface BattleShip {
+
+  void fire();
+
+  void move();
+
+}

adapter/src/main/java/com/iluwatar/adapter/Captain.java

@@ -0,0 +1,33 @@
+package com.iluwatar.adapter;
+
+/**
+ * The Captain uses {@link BattleShip} to fight. <br>
+ * This is the client in the pattern.
+ */
+public class Captain implements BattleShip {
+
+  private BattleShip battleship;
+
+  public Captain() {
+
+  }
+
+  public Captain(BattleShip battleship) {
+    this.battleship = battleship;
+  }
+
+  public void setBattleship(BattleShip battleship) {
+    this.battleship = battleship;
+  }
+
+  @Override
+  public void fire() {
+    battleship.fire();
+  }
+
+  @Override
+  public void move() {
+    battleship.move();
+  }
+
+}

adapter/src/main/java/com/iluwatar/adapter/Engineer.java

@@ -1,12 +0,0 @@
-package com.iluwatar.adapter;
-
-/**
- * 
- * Engineers can operate devices.
- * 
- */
-public interface Engineer {
-
-	void operateDevice();
-
-}

adapter/src/main/java/com/iluwatar/adapter/FishingBoat.java

@@ -0,0 +1,18 @@
+package com.iluwatar.adapter;
+
+/**
+ *
+ * Device class (adaptee in the pattern). We want to reuse this class
+ *
+ */
+public class FishingBoat {
+
+  public void sail() {
+    System.out.println("The Boat is moving to that place");
+  }
+
+  public void fish() {
+    System.out.println("fishing ...");
+  }
+
+}

adapter/src/main/java/com/iluwatar/adapter/GnomeEngineer.java

@@ -1,24 +0,0 @@
-package com.iluwatar.adapter;
-
-/**
- * 
- * Adapter class. Adapts the interface of the device ({@link GoblinGlider}) into
- * {@link Engineer} interface expected by the client ({@link GnomeEngineeringManager}).
- * 
- */
-public class GnomeEngineer implements Engineer {
-
-	private GoblinGlider glider;
-
-	public GnomeEngineer() {
-		glider = new GoblinGlider();
-	}
-
-	@Override
-	public void operateDevice() {
-		glider.attachGlider();
-		glider.gainSpeed();
-		glider.takeOff();
-	}
-
-}

adapter/src/main/java/com/iluwatar/adapter/GnomeEngineeringManager.java

@@ -1,20 +0,0 @@
-package com.iluwatar.adapter;
-
-/**
- * 
- * GnomeEngineering manager uses {@link Engineer} to operate devices.
- * 
- */
-public class GnomeEngineeringManager implements Engineer {
-
-	private Engineer engineer;
-
-	public GnomeEngineeringManager() {
-		engineer = new GnomeEngineer();
-	}
-
-	@Override
-	public void operateDevice() {
-		engineer.operateDevice();
-	}
-}

adapter/src/main/java/com/iluwatar/adapter/GoblinGlider.java

@@ -1,21 +0,0 @@
-package com.iluwatar.adapter;
-
-/**
- * 
- * Device class (adaptee in the pattern).
- * 
- */
-public class GoblinGlider {
-
-	public void attachGlider() {
-		System.out.println("Glider attached.");
-	}
-
-	public void gainSpeed() {
-		System.out.println("Gaining speed.");
-	}
-
-	public void takeOff() {
-		System.out.println("Lift-off!");
-	}
-}

adapter/src/test/java/com/iluwatar/adapter/AdapterPatternTest.java

@@ -0,0 +1,61 @@
+package com.iluwatar.adapter;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Test class
+ * 
+ */
+public class AdapterPatternTest {
+
+  private Map<String, Object> beans;
+
+  private static final String BATTLESHIP_BEAN = "engineer";
+
+  private static final String CAPTAIN_BEAN = "captain";
+
+  /**
+   * This method runs before the test execution and sets the bean objects in the beans Map.
+   */
+  @Before
+  public void setup() {
+    beans = new HashMap<>();
+
+    BattleFishingBoat battleFishingBoat = spy(new BattleFishingBoat());
+    beans.put(BATTLESHIP_BEAN, battleFishingBoat);
+
+    Captain captain = new Captain();
+    captain.setBattleship((BattleFishingBoat) beans.get(BATTLESHIP_BEAN));
+    beans.put(CAPTAIN_BEAN, captain);
+  }
+
+  /**
+   * This test asserts that when we use the move() method on a captain bean(client), it is
+   * internally calling move method on the battleship object. The Adapter ({@link BattleFishingBoat}
+   * ) converts the interface of the target class ( {@link FishingBoat}) into a suitable one
+   * expected by the client ({@link Captain} ).
+   */
+  @Test
+  public void testAdapter() {
+    BattleShip captain = (BattleShip) beans.get(CAPTAIN_BEAN);
+
+    // when captain moves
+    captain.move();
+
+    // the captain internally calls the battleship object to move
+    BattleShip battleship = (BattleShip) beans.get(BATTLESHIP_BEAN);
+    verify(battleship).move();
+
+    // same with above with firing
+    captain.fire();
+    verify(battleship).fire();
+
+  }
+}

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

@@ -1,19 +0,0 @@
-package com.iluwatar.adapter;
-
-import org.junit.Test;
-
-import com.iluwatar.adapter.App;
-
-/**
- * 
- * Application test
- *
- */
-public class AppTest {
-
-	@Test
-	public void test() {
-		String[] args = {};
-		App.main(args);
-	}
-}

async-method-invocation/index.md

@@ -4,7 +4,10 @@ title: Async Method Invocation
 folder: async-method-invocation
 permalink: /patterns/async-method-invocation/
 categories: Concurrency
-tags: Java
+tags:
+ - Java
+ - Difficulty-Intermediate
+ - Functional
 ---
 
 **Intent:** Asynchronous method invocation is pattern where the calling thread

async-method-invocation/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.7.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>async-method-invocation</artifactId>
   <dependencies>
@@ -14,5 +14,10 @@
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/App.java

@@ -5,22 +5,22 @@ import java.util.concurrent.Callable;
 /**
  * This application demonstrates the async method invocation pattern. Key parts of the pattern are
  * <code>AsyncResult</code> which is an intermediate container for an asynchronously evaluated value,
- * <code>AsyncCallback</code> which can be provided to be executed on task completion and
- * <code>AsyncExecutor</code> that manages the execution of the async tasks.
+ * <code>AsyncCallback</code> which can be provided to be executed on task completion and <code>AsyncExecutor</code>
+ * that manages the execution of the async tasks.
  * <p>
- * The main method shows example flow of async invocations. The main thread starts multiple tasks with
- * variable durations and then continues its own work. When the main thread has done it's job it collects
- * the results of the async tasks. Two of the tasks are handled with callbacks, meaning the callbacks are
- * executed immediately when the tasks complete.
+ * The main method shows example flow of async invocations. The main thread starts multiple tasks with variable
+ * durations and then continues its own work. When the main thread has done it's job it collects the results of the
+ * async tasks. Two of the tasks are handled with callbacks, meaning the callbacks are executed immediately when the
+ * tasks complete.
  * <p>
- * Noteworthy difference of thread usage between the async results and callbacks is that the async results
- * are collected in the main thread but the callbacks are executed within the worker threads. This should be
- * noted when working with thread pools.
+ * Noteworthy difference of thread usage between the async results and callbacks is that the async results are collected
+ * in the main thread but the callbacks are executed within the worker threads. This should be noted when working with
+ * thread pools.
  * <p>
- * Java provides its own implementations of async method invocation pattern. FutureTask, CompletableFuture
- * and ExecutorService are the real world implementations of this pattern. But due to the nature of parallel
- * programming, the implementations are not trivial. This example does not take all possible scenarios into
- * account but rather provides a simple version that helps to understand the pattern.
+ * Java provides its own implementations of async method invocation pattern. FutureTask, CompletableFuture and
+ * ExecutorService are the real world implementations of this pattern. But due to the nature of parallel programming,
+ * the implementations are not trivial. This example does not take all possible scenarios into account but rather
+ * provides a simple version that helps to understand the pattern.
  *
  * @see AsyncResult
  * @see AsyncCallback
@@ -32,66 +32,72 @@ import java.util.concurrent.Callable;
  */
 public class App {
 
-	public static void main(String[] args) throws Exception {
-		// construct a new executor that will run async tasks
-		AsyncExecutor executor = new ThreadAsyncExecutor();
+  /**
+   * Program entry point
+   */
+  public static void main(String[] args) throws Exception {
+    // construct a new executor that will run async tasks
+    AsyncExecutor executor = new ThreadAsyncExecutor();
 
-		// start few async tasks with varying processing times, two last with callback handlers
-		AsyncResult<Integer> asyncResult1 = executor.startProcess(lazyval(10, 500));
-		AsyncResult<String> asyncResult2 = executor.startProcess(lazyval("test", 300));
-		AsyncResult<Long> asyncResult3 = executor.startProcess(lazyval(50L, 700));
-		AsyncResult<Integer> asyncResult4 = executor.startProcess(lazyval(20, 400), callback("Callback result 4"));
-		AsyncResult<String> asyncResult5 = executor.startProcess(lazyval("callback", 600), callback("Callback result 5"));
+    // start few async tasks with varying processing times, two last with callback handlers
+    AsyncResult<Integer> asyncResult1 = executor.startProcess(lazyval(10, 500));
+    AsyncResult<String> asyncResult2 = executor.startProcess(lazyval("test", 300));
+    AsyncResult<Long> asyncResult3 = executor.startProcess(lazyval(50L, 700));
+    AsyncResult<Integer> asyncResult4 = executor.startProcess(lazyval(20, 400), callback("Callback result 4"));
+    AsyncResult<String> asyncResult5 = executor.startProcess(lazyval("callback", 600), callback("Callback result 5"));
 
-		// emulate processing in the current thread while async tasks are running in their own threads
-		Thread.sleep(350); // Oh boy I'm working hard here
-		log("Some hard work done");
+    // emulate processing in the current thread while async tasks are running in their own threads
+    Thread.sleep(350); // Oh boy I'm working hard here
+    log("Some hard work done");
 
-		// wait for completion of the tasks
-		Integer result1 = executor.endProcess(asyncResult1);
-		String result2 = executor.endProcess(asyncResult2);
-		Long result3 = executor.endProcess(asyncResult3);
-		asyncResult4.await();
-		asyncResult5.await();
+    // wait for completion of the tasks
+    Integer result1 = executor.endProcess(asyncResult1);
+    String result2 = executor.endProcess(asyncResult2);
+    Long result3 = executor.endProcess(asyncResult3);
+    asyncResult4.await();
+    asyncResult5.await();
 
-		// log the results of the tasks, callbacks log immediately when complete
-		log("Result 1: " + result1);
-		log("Result 2: " + result2);
-		log("Result 3: " + result3);
-	}
+    // log the results of the tasks, callbacks log immediately when complete
+    log("Result 1: " + result1);
+    log("Result 2: " + result2);
+    log("Result 3: " + result3);
+  }
 
-	/**
-	 * Creates a callable that lazily evaluates to given value with artificial delay.
-	 *
-	 * @param value value to evaluate
-	 * @param delayMillis artificial delay in milliseconds
-	 * @return new callable for lazy evaluation
-	 */
-	private static <T> Callable<T> lazyval(T value, long delayMillis) {
-		return () -> {
-			Thread.sleep(delayMillis);
-			log("Task completed with: " + value);
-			return value;
-		};
-	}
+  /**
+   * Creates a callable that lazily evaluates to given value with artificial delay.
+   *
+   * @param value
+   *          value to evaluate
+   * @param delayMillis
+   *          artificial delay in milliseconds
+   * @return new callable for lazy evaluation
+   */
+  private static <T> Callable<T> lazyval(T value, long delayMillis) {
+    return () -> {
+      Thread.sleep(delayMillis);
+      log("Task completed with: " + value);
+      return value;
+    };
+  }
 
-	/**
-	 * Creates a simple callback that logs the complete status of the async result.
-	 *
-	 * @param name callback name
-	 * @return new async callback
-	 */
-	private static <T> AsyncCallback<T> callback(String name) {
-		return (value, ex) -> {
-			if (ex.isPresent()) {
-				log(name + " failed: " + ex.map(Exception::getMessage).orElse(""));
-			} else {
-				log(name + ": " + value);
-			}
-		};
-	}
+  /**
+   * Creates a simple callback that logs the complete status of the async result.
+   *
+   * @param name
+   *          callback name
+   * @return new async callback
+   */
+  private static <T> AsyncCallback<T> callback(String name) {
+    return (value, ex) -> {
+      if (ex.isPresent()) {
+        log(name + " failed: " + ex.map(Exception::getMessage).orElse(""));
+      } else {
+        log(name + ": " + value);
+      }
+    };
+  }
 
-	private static void log(String msg) {
-		System.out.println(String.format("[%1$-10s] - %2$s", Thread.currentThread().getName(), msg));
-	}
+  private static void log(String msg) {
+    System.out.println(String.format("[%1$-10s] - %2$s", Thread.currentThread().getName(), msg));
+  }
 }

async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncCallback.java

@@ -11,12 +11,11 @@ import java.util.Optional;
  */
 public interface AsyncCallback<T> {
 
-	/**
-	 * Complete handler which is executed when async task is completed or fails execution.
-	 *
-	 * @param value the evaluated value from async task, undefined when execution fails
-	 * @param ex empty value if execution succeeds, some exception if executions fails
-	 */
-	void onComplete(T value, Optional<Exception> ex);
-
+  /**
+   * Complete handler which is executed when async task is completed or fails execution.
+   *
+   * @param value the evaluated value from async task, undefined when execution fails
+   * @param ex empty value if execution succeeds, some exception if executions fails
+   */
+  void onComplete(T value, Optional<Exception> ex);
 }

async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncExecutor.java

@@ -10,33 +10,32 @@ import java.util.concurrent.ExecutionException;
  */
 public interface AsyncExecutor {
 
-	/**
-	 * Starts processing of an async task. Returns immediately with async result.
-	 *
-	 * @param task task to be executed asynchronously
-	 * @return async result for the task
-	 */
-	<T> AsyncResult<T> startProcess(Callable<T> task);
+  /**
+   * Starts processing of an async task. Returns immediately with async result.
+   *
+   * @param task task to be executed asynchronously
+   * @return async result for the task
+   */
+  <T> AsyncResult<T> startProcess(Callable<T> task);
 
-	/**
-	 * Starts processing of an async task. Returns immediately with async result. Executes callback
-	 * when the task is completed.
-	 *
-	 * @param task task to be executed asynchronously
-	 * @param callback callback to be executed on task completion
-	 * @return async result for the task
-	 */
-	<T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback);
-
-	/**
-	 * Ends processing of an async task. Blocks the current thread if necessary and returns the
-	 * evaluated value of the completed task.
-	 *
-	 * @param asyncResult async result of a task
-	 * @return evaluated value of the completed task
-	 * @throws ExecutionException if execution has failed, containing the root cause
-	 * @throws InterruptedException if the execution is interrupted
-	 */
-	<T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException;
+  /**
+   * Starts processing of an async task. Returns immediately with async result. Executes callback
+   * when the task is completed.
+   *
+   * @param task task to be executed asynchronously
+   * @param callback callback to be executed on task completion
+   * @return async result for the task
+   */
+  <T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback);
 
+  /**
+   * Ends processing of an async task. Blocks the current thread if necessary and returns the
+   * evaluated value of the completed task.
+   *
+   * @param asyncResult async result of a task
+   * @return evaluated value of the completed task
+   * @throws ExecutionException if execution has failed, containing the root cause
+   * @throws InterruptedException if the execution is interrupted
+   */
+  <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException;
 }

async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncResult.java

@@ -5,31 +5,29 @@ import java.util.concurrent.ExecutionException;
 /**
  * 
  * AsyncResult interface
- *
- * @param <T>
  */
 public interface AsyncResult<T> {
 
-	/**
-	 * Status of the async task execution.
-	 *
-	 * @return <code>true</code> if execution is completed or failed
-	 */
-	boolean isCompleted();
+  /**
+   * Status of the async task execution.
+   *
+   * @return <code>true</code> if execution is completed or failed
+   */
+  boolean isCompleted();
 
-	/**
-	 * Gets the value of completed async task.
-	 *
-	 * @return evaluated value or throws ExecutionException if execution has failed
-	 * @throws ExecutionException if execution has failed, containing the root cause
-	 * @throws IllegalStateException if execution is not completed
-	 */
-	T getValue() throws ExecutionException;
+  /**
+   * Gets the value of completed async task.
+   *
+   * @return evaluated value or throws ExecutionException if execution has failed
+   * @throws ExecutionException if execution has failed, containing the root cause
+   * @throws IllegalStateException if execution is not completed
+   */
+  T getValue() throws ExecutionException;
 
-	/**
-	 * Blocks the current thread until the async task is completed.
-	 *
-	 * @throws InterruptedException if the execution is interrupted
-	 */
-	void await() throws InterruptedException;
+  /**
+   * Blocks the current thread until the async task is completed.
+   *
+   * @throws InterruptedException if the execution is interrupted
+   */
+  void await() throws InterruptedException;
 }

async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutor.java

@@ -12,116 +12,117 @@ import java.util.concurrent.atomic.AtomicInteger;
  */
 public class ThreadAsyncExecutor implements AsyncExecutor {
 
-	/** Index for thread naming */
-	private final AtomicInteger idx = new AtomicInteger(0);
+  /** Index for thread naming */
+  private final AtomicInteger idx = new AtomicInteger(0);
 
-	@Override
-	public <T> AsyncResult<T> startProcess(Callable<T> task) {
-		return startProcess(task, null);
-	}
+  @Override
+  public <T> AsyncResult<T> startProcess(Callable<T> task) {
+    return startProcess(task, null);
+  }
 
-	@Override
-	public <T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback) {
-		CompletableResult<T> result = new CompletableResult<>(callback);
-		new Thread(() -> {
-			try {
-				result.setValue(task.call());
-			} catch (Exception ex) {
-				result.setException(ex);
-			}
-		}, "executor-" + idx.incrementAndGet()).start();
-		return result;
-	}
+  @Override
+  public <T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback) {
+    CompletableResult<T> result = new CompletableResult<>(callback);
+    new Thread(() -> {
+      try {
+        result.setValue(task.call());
+      } catch (Exception ex) {
+        result.setException(ex);
+      }
+    } , "executor-" + idx.incrementAndGet()).start();
+    return result;
+  }
 
-	@Override
-	public <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException {
-		if (asyncResult.isCompleted()) {
-			return asyncResult.getValue();
-		} else {
-			asyncResult.await();
-			return asyncResult.getValue();
-		}
-	}
+  @Override
+  public <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException {
+    if (asyncResult.isCompleted()) {
+      return asyncResult.getValue();
+    } else {
+      asyncResult.await();
+      return asyncResult.getValue();
+    }
+  }
 
-	/**
-	 * Simple implementation of async result that allows completing it successfully with a value
-	 * or exceptionally with an exception. A really simplified version from its real life cousins
-	 * FutureTask and CompletableFuture.
-	 *
-	 * @see java.util.concurrent.FutureTask
-	 * @see java.util.concurrent.CompletableFuture
-	 */
-	private static class CompletableResult<T> implements AsyncResult<T> {
+  /**
+   * Simple implementation of async result that allows completing it successfully with a value or exceptionally with an
+   * exception. A really simplified version from its real life cousins FutureTask and CompletableFuture.
+   *
+   * @see java.util.concurrent.FutureTask
+   * @see java.util.concurrent.CompletableFuture
+   */
+  private static class CompletableResult<T> implements AsyncResult<T> {
 
-		static final int RUNNING = 1;
-		static final int FAILED = 2;
-		static final int COMPLETED = 3;
+    static final int RUNNING = 1;
+    static final int FAILED = 2;
+    static final int COMPLETED = 3;
 
-		final Object lock;
-		final Optional<AsyncCallback<T>> callback;
+    final Object lock;
+    final Optional<AsyncCallback<T>> callback;
 
-		volatile int state = RUNNING;
-		T value;
-		Exception exception;
+    volatile int state = RUNNING;
+    T value;
+    Exception exception;
 
-		CompletableResult(AsyncCallback<T> callback) {
-			this.lock = new Object();
-			this.callback = Optional.ofNullable(callback);
-		}
+    CompletableResult(AsyncCallback<T> callback) {
+      this.lock = new Object();
+      this.callback = Optional.ofNullable(callback);
+    }
 
-		/**
-		 * Sets the value from successful execution and executes callback if available. Notifies
-		 * any thread waiting for completion.
-		 *
-		 * @param value value of the evaluated task
-		 */
-		void setValue(T value) {
-			this.value = value;
-			this.state = COMPLETED;
-			this.callback.ifPresent(ac -> ac.onComplete(value, Optional.<Exception>empty()));
-			synchronized (lock) {
-				lock.notifyAll();
-			}
-		}
+    /**
+     * Sets the value from successful execution and executes callback if available. Notifies any thread waiting for
+     * completion.
+     *
+     * @param value
+     *          value of the evaluated task
+     */
+    void setValue(T value) {
+      this.value = value;
+      this.state = COMPLETED;
+      this.callback.ifPresent(ac -> ac.onComplete(value, Optional.<Exception>empty()));
+      synchronized (lock) {
+        lock.notifyAll();
+      }
+    }
 
-		/**
-		 * Sets the exception from failed execution and executes callback if available. Notifies
-		 * any thread waiting for completion.
-		 *
-		 * @param exception exception of the failed task
-		 */
-		void setException(Exception exception) {
-			this.exception = exception;
-			this.state = FAILED;
-			this.callback.ifPresent(ac -> ac.onComplete(null, Optional.of(exception)));
-			synchronized (lock) {
-				lock.notifyAll();
-			}
-		}
+    /**
+     * Sets the exception from failed execution and executes callback if available. Notifies any thread waiting for
+     * completion.
+     *
+     * @param exception
+     *          exception of the failed task
+     */
+    void setException(Exception exception) {
+      this.exception = exception;
+      this.state = FAILED;
+      this.callback.ifPresent(ac -> ac.onComplete(null, Optional.of(exception)));
+      synchronized (lock) {
+        lock.notifyAll();
+      }
+    }
 
-		@Override
-		public boolean isCompleted() {
-			return (state > RUNNING);
-		}
+    @Override
+    public boolean isCompleted() {
+      return state > RUNNING;
+    }
 
-		@Override
-		public T getValue() throws ExecutionException {
-			if (state == COMPLETED) {
-				return value;
-			} else if (state == FAILED) {
-				throw new ExecutionException(exception);
-			} else {
-				throw new IllegalStateException("Execution not completed yet");
-			}
-		}
+    @Override
+    public T getValue() throws ExecutionException {
+      if (state == COMPLETED) {
+        return value;
+      } else if (state == FAILED) {
+        throw new ExecutionException(exception);
+      } else {
+        throw new IllegalStateException("Execution not completed yet");
+      }
+    }
 
-		@Override
-		public void await() throws InterruptedException {
-			synchronized (lock) {
-				if (!isCompleted()) {
-					lock.wait();
-				}
-			}
-		}
-	}
+    @Override
+    public void await() throws InterruptedException {
+      synchronized (lock) {
+        if (!isCompleted()) {
+          lock.wait();
+        }
+      }
+    }
+  }
 }

async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/AppTest.java

@@ -9,10 +9,9 @@ import org.junit.Test;
  */
 public class AppTest {
 
-	@Test
-	public void test() throws Exception {
-		String[] args = {};
-		App.main(args);
-	}
-
+  @Test
+  public void test() throws Exception {
+    String[] args = {};
+    App.main(args);
+  }
 }

async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutorTest.java

@@ -0,0 +1,290 @@
+package com.iluwatar.async.method.invocation;
+
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Matchers;
+
+import java.util.Optional;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+
+import static org.junit.Assert.*;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.*;
+import static org.mockito.internal.verification.VerificationModeFactory.times;
+
+/**
+ * Date: 12/6/15 - 10:49 AM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class ThreadAsyncExecutorTest {
+
+  /**
+   * Test used to verify the happy path of {@link ThreadAsyncExecutor#startProcess(Callable)}
+   */
+  @Test(timeout = 3000)
+  public void testSuccessfulTaskWithoutCallback() throws Exception {
+    // Instantiate a new executor and start a new 'null' task ...
+    final ThreadAsyncExecutor executor = new ThreadAsyncExecutor();
+
+    final Object result = new Object();
+    final Callable<Object> task = mock(Callable.class);
+    when(task.call()).thenReturn(result);
+
+    final AsyncResult<Object> asyncResult = executor.startProcess(task);
+    assertNotNull(asyncResult);
+    asyncResult.await(); // Prevent timing issues, and wait until the result is available
+    assertTrue(asyncResult.isCompleted());
+
+    // Our task should only execute once ...
+    verify(task, times(1)).call();
+
+    // ... and the result should be exactly the same object
+    assertSame(result, asyncResult.getValue());
+  }
+
+  /**
+   * Test used to verify the happy path of {@link ThreadAsyncExecutor#startProcess(Callable, AsyncCallback)}
+   */
+  @Test(timeout = 3000)
+  public void testSuccessfulTaskWithCallback() throws Exception {
+    // Instantiate a new executor and start a new 'null' task ...
+    final ThreadAsyncExecutor executor = new ThreadAsyncExecutor();
+
+    final Object result = new Object();
+    final Callable<Object> task = mock(Callable.class);
+    when(task.call()).thenReturn(result);
+
+    final AsyncCallback callback = mock(AsyncCallback.class);
+    final AsyncResult<Object> asyncResult = executor.startProcess(task, callback);
+    assertNotNull(asyncResult);
+    asyncResult.await(); // Prevent timing issues, and wait until the result is available
+    assertTrue(asyncResult.isCompleted());
+
+    // Our task should only execute once ...
+    verify(task, times(1)).call();
+
+    // ... same for the callback, we expect our object
+    final ArgumentCaptor<Optional<Exception>> optionalCaptor = ArgumentCaptor.forClass((Class) Optional.class);
+    verify(callback, times(1)).onComplete(eq(result), optionalCaptor.capture());
+
+    final Optional<Exception> optionalException = optionalCaptor.getValue();
+    assertNotNull(optionalException);
+    assertFalse(optionalException.isPresent());
+
+    // ... and the result should be exactly the same object
+    assertSame(result, asyncResult.getValue());
+  }
+
+  /**
+   * Test used to verify the happy path of {@link ThreadAsyncExecutor#startProcess(Callable)} when a task takes a while
+   * to execute
+   */
+  @Test(timeout = 5000)
+  public void testLongRunningTaskWithoutCallback() throws Exception {
+    // Instantiate a new executor and start a new 'null' task ...
+    final ThreadAsyncExecutor executor = new ThreadAsyncExecutor();
+
+    final Object result = new Object();
+    final Callable<Object> task = mock(Callable.class);
+    when(task.call()).thenAnswer(i -> {
+      Thread.sleep(1500);
+      return result;
+    });
+
+    final AsyncResult<Object> asyncResult = executor.startProcess(task);
+    assertNotNull(asyncResult);
+    assertFalse(asyncResult.isCompleted());
+
+    try {
+      asyncResult.getValue();
+      fail("Expected IllegalStateException when calling AsyncResult#getValue on a non-completed task");
+    } catch (IllegalStateException e) {
+      assertNotNull(e.getMessage());
+    }
+
+    // Our task should only execute once, but it can take a while ...
+    verify(task, timeout(3000).times(1)).call();
+
+    // Prevent timing issues, and wait until the result is available
+    asyncResult.await();
+    assertTrue(asyncResult.isCompleted());
+    verifyNoMoreInteractions(task);
+
+    // ... and the result should be exactly the same object
+    assertSame(result, asyncResult.getValue());
+  }
+
+  /**
+   * Test used to verify the happy path of {@link ThreadAsyncExecutor#startProcess(Callable, AsyncCallback)} when a task
+   * takes a while to execute
+   */
+  @Test(timeout = 5000)
+  public void testLongRunningTaskWithCallback() throws Exception {
+    // Instantiate a new executor and start a new 'null' task ...
+    final ThreadAsyncExecutor executor = new ThreadAsyncExecutor();
+
+    final Object result = new Object();
+    final Callable<Object> task = mock(Callable.class);
+    when(task.call()).thenAnswer(i -> {
+      Thread.sleep(1500);
+      return result;
+    });
+
+    final AsyncCallback<Object> callback = mock(AsyncCallback.class);
+    final AsyncResult<Object> asyncResult = executor.startProcess(task, callback);
+    assertNotNull(asyncResult);
+    assertFalse(asyncResult.isCompleted());
+
+    verifyZeroInteractions(callback);
+
+    try {
+      asyncResult.getValue();
+      fail("Expected IllegalStateException when calling AsyncResult#getValue on a non-completed task");
+    } catch (IllegalStateException e) {
+      assertNotNull(e.getMessage());
+    }
+
+    // Our task should only execute once, but it can take a while ...
+    verify(task, timeout(3000).times(1)).call();
+
+    final ArgumentCaptor<Optional<Exception>> optionalCaptor = ArgumentCaptor.forClass((Class) Optional.class);
+    verify(callback, timeout(3000).times(1)).onComplete(eq(result), optionalCaptor.capture());
+
+    final Optional<Exception> optionalException = optionalCaptor.getValue();
+    assertNotNull(optionalException);
+    assertFalse(optionalException.isPresent());
+
+    // Prevent timing issues, and wait until the result is available
+    asyncResult.await();
+    assertTrue(asyncResult.isCompleted());
+    verifyNoMoreInteractions(task, callback);
+
+    // ... and the result should be exactly the same object
+    assertSame(result, asyncResult.getValue());
+  }
+
+  /**
+   * Test used to verify the happy path of {@link ThreadAsyncExecutor#startProcess(Callable)} when a task takes a while
+   * to execute, while waiting on the result using {@link ThreadAsyncExecutor#endProcess(AsyncResult)}
+   */
+  @Test(timeout = 5000)
+  public void testEndProcess() throws Exception {
+    // Instantiate a new executor and start a new 'null' task ...
+    final ThreadAsyncExecutor executor = new ThreadAsyncExecutor();
+
+    final Object result = new Object();
+    final Callable<Object> task = mock(Callable.class);
+    when(task.call()).thenAnswer(i -> {
+      Thread.sleep(1500);
+      return result;
+    });
+
+    final AsyncResult<Object> asyncResult = executor.startProcess(task);
+    assertNotNull(asyncResult);
+    assertFalse(asyncResult.isCompleted());
+
+    try {
+      asyncResult.getValue();
+      fail("Expected IllegalStateException when calling AsyncResult#getValue on a non-completed task");
+    } catch (IllegalStateException e) {
+      assertNotNull(e.getMessage());
+    }
+
+    assertSame(result, executor.endProcess(asyncResult));
+    verify(task, times(1)).call();
+    assertTrue(asyncResult.isCompleted());
+
+    // Calling end process a second time while already finished should give the same result
+    assertSame(result, executor.endProcess(asyncResult));
+    verifyNoMoreInteractions(task);
+  }
+
+  /**
+   * Test used to verify the behaviour of {@link ThreadAsyncExecutor#startProcess(Callable)} when the callable is 'null'
+   */
+  @Test(timeout = 3000)
+  public void testNullTask() throws Exception {
+    // Instantiate a new executor and start a new 'null' task ...
+    final ThreadAsyncExecutor executor = new ThreadAsyncExecutor();
+    final AsyncResult<Object> asyncResult = executor.startProcess(null);
+
+    assertNotNull("The AsyncResult should not be 'null', even though the task was 'null'.", asyncResult);
+    asyncResult.await(); // Prevent timing issues, and wait until the result is available
+    assertTrue(asyncResult.isCompleted());
+
+    try {
+      asyncResult.getValue();
+      fail("Expected ExecutionException with NPE as cause");
+    } catch (final ExecutionException e) {
+      assertNotNull(e.getMessage());
+      assertNotNull(e.getCause());
+      assertEquals(NullPointerException.class, e.getCause().getClass());
+    }
+
+  }
+
+  /**
+   * Test used to verify the behaviour of {@link ThreadAsyncExecutor#startProcess(Callable, AsyncCallback)} when the
+   * callable is 'null', but the asynchronous callback is provided
+   */
+  @Test(timeout = 3000)
+  public void testNullTaskWithCallback() throws Exception {
+    // Instantiate a new executor and start a new 'null' task ...
+    final ThreadAsyncExecutor executor = new ThreadAsyncExecutor();
+    final AsyncCallback<Object> callback = mock(AsyncCallback.class);
+    final AsyncResult<Object> asyncResult = executor.startProcess(null, callback);
+
+    assertNotNull("The AsyncResult should not be 'null', even though the task was 'null'.", asyncResult);
+    asyncResult.await(); // Prevent timing issues, and wait until the result is available
+    assertTrue(asyncResult.isCompleted());
+
+    final ArgumentCaptor<Optional<Exception>> optionalCaptor = ArgumentCaptor.forClass((Class) Optional.class);
+    verify(callback, times(1)).onComplete(Matchers.isNull(), optionalCaptor.capture());
+
+    final Optional<Exception> optionalException = optionalCaptor.getValue();
+    assertNotNull(optionalException);
+    assertTrue(optionalException.isPresent());
+
+    final Exception exception = optionalException.get();
+    assertNotNull(exception);
+    assertEquals(NullPointerException.class, exception.getClass());
+
+    try {
+      asyncResult.getValue();
+      fail("Expected ExecutionException with NPE as cause");
+    } catch (final ExecutionException e) {
+      assertNotNull(e.getMessage());
+      assertNotNull(e.getCause());
+      assertEquals(NullPointerException.class, e.getCause().getClass());
+    }
+
+  }
+
+  /**
+   * Test used to verify the behaviour of {@link ThreadAsyncExecutor#startProcess(Callable, AsyncCallback)} when both
+   * the callable and the asynchronous callback are 'null'
+   */
+  @Test(timeout = 3000)
+  public void testNullTaskWithNullCallback() throws Exception {
+    // Instantiate a new executor and start a new 'null' task ...
+    final ThreadAsyncExecutor executor = new ThreadAsyncExecutor();
+    final AsyncResult<Object> asyncResult = executor.startProcess(null, null);
+
+    assertNotNull("The AsyncResult should not be 'null', even though the task and callback were 'null'.", asyncResult);
+    asyncResult.await(); // Prevent timing issues, and wait until the result is available
+    assertTrue(asyncResult.isCompleted());
+
+    try {
+      asyncResult.getValue();
+      fail("Expected ExecutionException with NPE as cause");
+    } catch (final ExecutionException e) {
+      assertNotNull(e.getMessage());
+      assertNotNull(e.getCause());
+      assertEquals(NullPointerException.class, e.getCause().getClass());
+    }
+
+  }
+
+}

bridge/index.md

@@ -7,8 +7,11 @@ categories: Structural
 tags:
  - Java
  - Gang Of Four
+ - Difficulty-Intermediate
 ---
 
+**Also known as:** Handle/Body
+
 **Intent:** Decouple an abstraction from its implementation so that the two can
 vary independently.
 

bridge/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.7.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>bridge</artifactId>
   <dependencies>
@@ -14,5 +14,10 @@
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

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

@@ -2,41 +2,38 @@ package com.iluwatar.bridge;
 
 /**
  * 
- * The Bridge pattern can also be thought of as two layers of abstraction. With Bridge, 
- * you can decouple an abstraction from its implementation so that the two can vary independently.
+ * The Bridge pattern can also be thought of as two layers of abstraction. With Bridge, you can
+ * decouple an abstraction from its implementation so that the two can vary independently.
  * <p>
- * In Bridge pattern both abstraction ({@link MagicWeapon}) and implementation
- * ({@link MagicWeaponImpl}) have their own class hierarchies. The interface of the
- * implementations can be changed without affecting the clients.
+ * In Bridge pattern both abstraction ({@link MagicWeapon}) and implementation (
+ * {@link MagicWeaponImpl}) have their own class hierarchies. The interface of the implementations
+ * can be changed without affecting the clients.
  * 
  */
 public class App {
 
-	/**
-	 * Program entry point
-	 * @param args command line args
-	 */
-	public static void main(String[] args) {
-		BlindingMagicWeapon blindingMagicWeapon = new BlindingMagicWeapon(
-				new Excalibur());
-		blindingMagicWeapon.wield();
-		blindingMagicWeapon.blind();
-		blindingMagicWeapon.swing();
-		blindingMagicWeapon.unwield();
+  /**
+   * Program entry point
+   * 
+   * @param args command line args
+   */
+  public static void main(String[] args) {
+    BlindingMagicWeapon blindingMagicWeapon = new BlindingMagicWeapon(new Excalibur());
+    blindingMagicWeapon.wield();
+    blindingMagicWeapon.blind();
+    blindingMagicWeapon.swing();
+    blindingMagicWeapon.unwield();
 
-		FlyingMagicWeapon flyingMagicWeapon = new FlyingMagicWeapon(
-				new Mjollnir());
-		flyingMagicWeapon.wield();
-		flyingMagicWeapon.fly();
-		flyingMagicWeapon.swing();
-		flyingMagicWeapon.unwield();
+    FlyingMagicWeapon flyingMagicWeapon = new FlyingMagicWeapon(new Mjollnir());
+    flyingMagicWeapon.wield();
+    flyingMagicWeapon.fly();
+    flyingMagicWeapon.swing();
+    flyingMagicWeapon.unwield();
 
-		SoulEatingMagicWeapon soulEatingMagicWeapon = new SoulEatingMagicWeapon(
-				new Stormbringer());
-		soulEatingMagicWeapon.wield();
-		soulEatingMagicWeapon.swing();
-		soulEatingMagicWeapon.eatSoul();
-		soulEatingMagicWeapon.unwield();
-
-	}
+    SoulEatingMagicWeapon soulEatingMagicWeapon = new SoulEatingMagicWeapon(new Stormbringer());
+    soulEatingMagicWeapon.wield();
+    soulEatingMagicWeapon.swing();
+    soulEatingMagicWeapon.eatSoul();
+    soulEatingMagicWeapon.unwield();
+  }
 }

bridge/src/main/java/com/iluwatar/bridge/BlindingMagicWeapon.java

@@ -7,32 +7,31 @@ package com.iluwatar.bridge;
  */
 public class BlindingMagicWeapon extends MagicWeapon {
 
-	public BlindingMagicWeapon(BlindingMagicWeaponImpl imp) {
-		super(imp);
-	}
+  public BlindingMagicWeapon(BlindingMagicWeaponImpl imp) {
+    super(imp);
+  }
 
-	@Override
-	public BlindingMagicWeaponImpl getImp() {
-		return (BlindingMagicWeaponImpl) imp;
-	}
+  @Override
+  public BlindingMagicWeaponImpl getImp() {
+    return (BlindingMagicWeaponImpl) imp;
+  }
 
-	@Override
-	public void wield() {
-		getImp().wieldImp();
-	}
+  @Override
+  public void wield() {
+    getImp().wieldImp();
+  }
 
-	@Override
-	public void swing() {
-		getImp().swingImp();
-	}
+  @Override
+  public void swing() {
+    getImp().swingImp();
+  }
 
-	@Override
-	public void unwield() {
-		getImp().unwieldImp();
-	}
-
-	public void blind() {
-		getImp().blindImp();
-	}
+  @Override
+  public void unwield() {
+    getImp().unwieldImp();
+  }
 
+  public void blind() {
+    getImp().blindImp();
+  }
 }

bridge/src/main/java/com/iluwatar/bridge/BlindingMagicWeaponImpl.java

@@ -7,6 +7,6 @@ package com.iluwatar.bridge;
  */
 public abstract class BlindingMagicWeaponImpl extends MagicWeaponImpl {
 
-	public abstract void blindImp();
+  public abstract void blindImp();
 
 }

bridge/src/main/java/com/iluwatar/bridge/Excalibur.java

@@ -7,25 +7,23 @@ package com.iluwatar.bridge;
  */
 public class Excalibur extends BlindingMagicWeaponImpl {
 
-	@Override
-	public void wieldImp() {
-		System.out.println("wielding Excalibur");
-	}
+  @Override
+  public void wieldImp() {
+    System.out.println("wielding Excalibur");
+  }
 
-	@Override
-	public void swingImp() {
-		System.out.println("swinging Excalibur");
-	}
+  @Override
+  public void swingImp() {
+    System.out.println("swinging Excalibur");
+  }
 
-	@Override
-	public void unwieldImp() {
-		System.out.println("unwielding Excalibur");
-	}
-
-	@Override
-	public void blindImp() {
-		System.out
-				.println("bright light streams from Excalibur blinding the enemy");
-	}
+  @Override
+  public void unwieldImp() {
+    System.out.println("unwielding Excalibur");
+  }
 
+  @Override
+  public void blindImp() {
+    System.out.println("bright light streams from Excalibur blinding the enemy");
+  }
 }

bridge/src/main/java/com/iluwatar/bridge/FlyingMagicWeapon.java

@@ -7,31 +7,31 @@ package com.iluwatar.bridge;
  */
 public class FlyingMagicWeapon extends MagicWeapon {
 
-	public FlyingMagicWeapon(FlyingMagicWeaponImpl imp) {
-		super(imp);
-	}
+  public FlyingMagicWeapon(FlyingMagicWeaponImpl imp) {
+    super(imp);
+  }
 
-	public FlyingMagicWeaponImpl getImp() {
-		return (FlyingMagicWeaponImpl) imp;
-	}
+  public FlyingMagicWeaponImpl getImp() {
+    return (FlyingMagicWeaponImpl) imp;
+  }
 
-	@Override
-	public void wield() {
-		getImp().wieldImp();
-	}
+  @Override
+  public void wield() {
+    getImp().wieldImp();
+  }
 
-	@Override
-	public void swing() {
-		getImp().swingImp();
-	}
+  @Override
+  public void swing() {
+    getImp().swingImp();
+  }
 
-	@Override
-	public void unwield() {
-		getImp().unwieldImp();
-	}
+  @Override
+  public void unwield() {
+    getImp().unwieldImp();
+  }
 
-	public void fly() {
-		getImp().flyImp();
-	}
+  public void fly() {
+    getImp().flyImp();
+  }
 
 }

bridge/src/main/java/com/iluwatar/bridge/FlyingMagicWeaponImpl.java

@@ -7,6 +7,6 @@ package com.iluwatar.bridge;
  */
 public abstract class FlyingMagicWeaponImpl extends MagicWeaponImpl {
 
-	public abstract void flyImp();
+  public abstract void flyImp();
 
 }

bridge/src/main/java/com/iluwatar/bridge/MagicWeapon.java

@@ -7,20 +7,19 @@ package com.iluwatar.bridge;
  */
 public abstract class MagicWeapon {
 
-	protected MagicWeaponImpl imp;
+  protected MagicWeaponImpl imp;
 
-	public MagicWeapon(MagicWeaponImpl imp) {
-		this.imp = imp;
-	}
+  public MagicWeapon(MagicWeaponImpl imp) {
+    this.imp = imp;
+  }
 
-	public abstract void wield();
+  public abstract void wield();
 
-	public abstract void swing();
+  public abstract void swing();
 
-	public abstract void unwield();
-
-	public MagicWeaponImpl getImp() {
-		return imp;
-	}
+  public abstract void unwield();
 
+  public MagicWeaponImpl getImp() {
+    return imp;
+  }
 }

bridge/src/main/java/com/iluwatar/bridge/MagicWeaponImpl.java

@@ -7,10 +7,10 @@ package com.iluwatar.bridge;
  */
 public abstract class MagicWeaponImpl {
 
-	public abstract void wieldImp();
+  public abstract void wieldImp();
 
-	public abstract void swingImp();
+  public abstract void swingImp();
 
-	public abstract void unwieldImp();
+  public abstract void unwieldImp();
 
 }

bridge/src/main/java/com/iluwatar/bridge/Mjollnir.java

@@ -7,25 +7,23 @@ package com.iluwatar.bridge;
  */
 public class Mjollnir extends FlyingMagicWeaponImpl {
 
-	@Override
-	public void wieldImp() {
-		System.out.println("wielding Mjollnir");
-	}
+  @Override
+  public void wieldImp() {
+    System.out.println("wielding Mjollnir");
+  }
 
-	@Override
-	public void swingImp() {
-		System.out.println("swinging Mjollnir");
-	}
+  @Override
+  public void swingImp() {
+    System.out.println("swinging Mjollnir");
+  }
 
-	@Override
-	public void unwieldImp() {
-		System.out.println("unwielding Mjollnir");
-	}
-
-	@Override
-	public void flyImp() {
-		System.out
-				.println("Mjollnir hits the enemy in the air and returns back to the owner's hand");
-	}
+  @Override
+  public void unwieldImp() {
+    System.out.println("unwielding Mjollnir");
+  }
 
+  @Override
+  public void flyImp() {
+    System.out.println("Mjollnir hits the enemy in the air and returns back to the owner's hand");
+  }
 }

bridge/src/main/java/com/iluwatar/bridge/SoulEatingMagicWeapon.java

@@ -7,32 +7,32 @@ package com.iluwatar.bridge;
  */
 public class SoulEatingMagicWeapon extends MagicWeapon {
 
-	public SoulEatingMagicWeapon(SoulEatingMagicWeaponImpl imp) {
-		super(imp);
-	}
+  public SoulEatingMagicWeapon(SoulEatingMagicWeaponImpl imp) {
+    super(imp);
+  }
 
-	@Override
-	public SoulEatingMagicWeaponImpl getImp() {
-		return (SoulEatingMagicWeaponImpl) imp;
-	}
+  @Override
+  public SoulEatingMagicWeaponImpl getImp() {
+    return (SoulEatingMagicWeaponImpl) imp;
+  }
 
-	@Override
-	public void wield() {
-		getImp().wieldImp();
-	}
+  @Override
+  public void wield() {
+    getImp().wieldImp();
+  }
 
-	@Override
-	public void swing() {
-		getImp().swingImp();
-	}
+  @Override
+  public void swing() {
+    getImp().swingImp();
+  }
 
-	@Override
-	public void unwield() {
-		getImp().unwieldImp();
-	}
+  @Override
+  public void unwield() {
+    getImp().unwieldImp();
+  }
 
-	public void eatSoul() {
-		getImp().eatSoulImp();
-	}
+  public void eatSoul() {
+    getImp().eatSoulImp();
+  }
 
 }

bridge/src/main/java/com/iluwatar/bridge/SoulEatingMagicWeaponImpl.java

@@ -7,6 +7,6 @@ package com.iluwatar.bridge;
  */
 public abstract class SoulEatingMagicWeaponImpl extends MagicWeaponImpl {
 
-	public abstract void eatSoulImp();
+  public abstract void eatSoulImp();
 
 }

bridge/src/main/java/com/iluwatar/bridge/Stormbringer.java

@@ -7,24 +7,23 @@ package com.iluwatar.bridge;
  */
 public class Stormbringer extends SoulEatingMagicWeaponImpl {
 
-	@Override
-	public void wieldImp() {
-		System.out.println("wielding Stormbringer");
-	}
+  @Override
+  public void wieldImp() {
+    System.out.println("wielding Stormbringer");
+  }
 
-	@Override
-	public void swingImp() {
-		System.out.println("swinging Stormbringer");
-	}
+  @Override
+  public void swingImp() {
+    System.out.println("swinging Stormbringer");
+  }
 
-	@Override
-	public void unwieldImp() {
-		System.out.println("unwielding Stormbringer");
-	}
-
-	@Override
-	public void eatSoulImp() {
-		System.out.println("Stormbringer devours the enemy's soul");
-	}
+  @Override
+  public void unwieldImp() {
+    System.out.println("unwielding Stormbringer");
+  }
 
+  @Override
+  public void eatSoulImp() {
+    System.out.println("Stormbringer devours the enemy's soul");
+  }
 }

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

@@ -2,8 +2,6 @@ package com.iluwatar.bridge;
 
 import org.junit.Test;
 
-import com.iluwatar.bridge.App;
-
 /**
  * 
  * Application test
@@ -11,9 +9,9 @@ import com.iluwatar.bridge.App;
  */
 public class AppTest {
 
-	@Test
-	public void test() {
-		String[] args = {};
-		App.main(args);
-	}
+  @Test
+  public void test() {
+    String[] args = {};
+    App.main(args);
+  }
 }

bridge/src/test/java/com/iluwatar/bridge/BlindingMagicWeaponTest.java

@@ -0,0 +1,33 @@
+package com.iluwatar.bridge;
+
+import org.junit.Test;
+
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.internal.verification.VerificationModeFactory.times;
+
+/**
+ * Date: 12/6/15 - 11:15 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class BlindingMagicWeaponTest extends MagicWeaponTest {
+
+  /**
+   * Invoke all possible actions on the weapon and check if the actions are executed on the actual
+   * underlying weapon implementation.
+   */
+  @Test
+  public void testExcalibur() throws Exception {
+    final Excalibur excalibur = spy(new Excalibur());
+    final BlindingMagicWeapon blindingMagicWeapon = new BlindingMagicWeapon(excalibur);
+
+    testBasicWeaponActions(blindingMagicWeapon, excalibur);
+
+    blindingMagicWeapon.blind();
+    verify(excalibur, times(1)).blindImp();
+    verifyNoMoreInteractions(excalibur);
+  }
+
+}

bridge/src/test/java/com/iluwatar/bridge/FlyingMagicWeaponTest.java

@@ -0,0 +1,33 @@
+package com.iluwatar.bridge;
+
+import org.junit.Test;
+
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.internal.verification.VerificationModeFactory.times;
+
+/**
+ * Date: 12/6/15 - 11:26 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class FlyingMagicWeaponTest extends MagicWeaponTest {
+
+  /**
+   * Invoke all possible actions on the weapon and check if the actions are executed on the actual
+   * underlying weapon implementation.
+   */
+  @Test
+  public void testMjollnir() throws Exception {
+    final Mjollnir mjollnir = spy(new Mjollnir());
+    final FlyingMagicWeapon flyingMagicWeapon = new FlyingMagicWeapon(mjollnir);
+
+    testBasicWeaponActions(flyingMagicWeapon, mjollnir);
+
+    flyingMagicWeapon.fly();
+    verify(mjollnir, times(1)).flyImp();
+    verifyNoMoreInteractions(mjollnir);
+  }
+
+}

bridge/src/test/java/com/iluwatar/bridge/MagicWeaponTest.java

@@ -0,0 +1,42 @@
+package com.iluwatar.bridge;
+
+import static org.junit.Assert.assertNotNull;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.internal.verification.VerificationModeFactory.times;
+
+/**
+ * Date: 12/6/15 - 11:28 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public abstract class MagicWeaponTest {
+
+  /**
+   * Invoke the basic actions of the given weapon, and test if the underlying weapon implementation
+   * is invoked
+   *
+   * @param weaponImpl The spied weapon implementation where actions are bridged to
+   * @param weapon               The weapon, handled by the app
+   */
+  protected final void testBasicWeaponActions(final MagicWeapon weapon,
+                                              final MagicWeaponImpl weaponImpl) {
+    assertNotNull(weapon);
+    assertNotNull(weaponImpl);
+    assertNotNull(weapon.getImp());
+
+    weapon.swing();
+    verify(weaponImpl, times(1)).swingImp();
+    verifyNoMoreInteractions(weaponImpl);
+
+    weapon.wield();
+    verify(weaponImpl, times(1)).wieldImp();
+    verifyNoMoreInteractions(weaponImpl);
+
+    weapon.unwield();
+    verify(weaponImpl, times(1)).unwieldImp();
+    verifyNoMoreInteractions(weaponImpl);
+
+  }
+
+}

bridge/src/test/java/com/iluwatar/bridge/SoulEatingMagicWeaponTest.java

@@ -0,0 +1,33 @@
+package com.iluwatar.bridge;
+
+import org.junit.Test;
+
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.internal.verification.VerificationModeFactory.times;
+
+/**
+ * Date: 12/6/15 - 11:43 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class SoulEatingMagicWeaponTest extends MagicWeaponTest {
+
+  /**
+   * Invoke all possible actions on the weapon and check if the actions are executed on the actual
+   * underlying weapon implementation.
+   */
+  @Test
+  public void testStormBringer() throws Exception {
+    final Stormbringer stormbringer = spy(new Stormbringer());
+    final SoulEatingMagicWeapon soulEatingMagicWeapon = new SoulEatingMagicWeapon(stormbringer);
+
+    testBasicWeaponActions(soulEatingMagicWeapon, stormbringer);
+
+    soulEatingMagicWeapon.eatSoul();
+    verify(stormbringer, times(1)).eatSoulImp();
+    verifyNoMoreInteractions(stormbringer);
+  }
+
+}

builder/index.md

@@ -7,6 +7,7 @@ categories: Creational
 tags:
  - Java
  - Gang Of Four
+ - Difficulty-Intermediate
 ---
 
 **Intent:** Separate the construction of a complex object from its

builder/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.7.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>builder</artifactId>
   <dependencies>

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

@@ -1,55 +1,55 @@
 package com.iluwatar.builder;
 
-import com.iluwatar. builder.Hero.HeroBuilder;
+import com.iluwatar.builder.Hero.HeroBuilder;
 
 /**
  * 
- * The intention of the Builder pattern is to find a solution to the telescoping 
- * constructor anti-pattern. The telescoping constructor anti-pattern occurs when the 
- * increase of object constructor parameter combination leads to an exponential list 
- * of constructors. Instead of using numerous constructors, the builder pattern uses 
- * another object, a builder, that receives each initialization parameter step by step 
- * and then returns the resulting constructed object at once.
+ * The intention of the Builder pattern is to find a solution to the telescoping constructor
+ * anti-pattern. The telescoping constructor anti-pattern occurs when the increase of object
+ * constructor parameter combination leads to an exponential list of constructors. Instead of using
+ * numerous constructors, the builder pattern uses another object, a builder, that receives each
+ * initialization parameter step by step and then returns the resulting constructed object at once.
  * <p>
- * The Builder pattern has another benefit. It can be used for objects that contain 
- * flat data (html code, SQL query, X.509 certificate...), that is to say, data that 
- * can't be easily edited. This type of data cannot be edited step by step and must 
- * be edited at once. The best way to construct such an object is to use a builder 
- * class.
+ * The Builder pattern has another benefit. It can be used for objects that contain flat data (html
+ * code, SQL query, X.509 certificate...), that is to say, data that can't be easily edited. This
+ * type of data cannot be edited step by step and must be edited at once. The best way to construct
+ * such an object is to use a builder class.
  * <p>
- * In this example we have the Builder pattern variation as described by Joshua Bloch in
- * Effective Java 2nd Edition.
+ * In this example we have the Builder pattern variation as described by Joshua Bloch in Effective
+ * Java 2nd Edition.
  * <p>
- * We want to build {@link Hero} objects, but its construction is complex because of the
- * many parameters needed. To aid the user we introduce {@link HeroBuilder} class.
- * {@link HeroBuilder} takes the minimum parameters to build {@link Hero} object in its
- * constructor. After that additional configuration for the {@link Hero} object can be
- * done using the fluent {@link HeroBuilder} interface. When configuration is ready the
- * build method is called to receive the final {@link Hero} object.
+ * We want to build {@link Hero} objects, but its construction is complex because of the many
+ * parameters needed. To aid the user we introduce {@link HeroBuilder} class. {@link HeroBuilder}
+ * takes the minimum parameters to build {@link Hero} object in its constructor. After that
+ * additional configuration for the {@link Hero} object can be done using the fluent
+ * {@link HeroBuilder} interface. When configuration is ready the build method is called to receive
+ * the final {@link Hero} object.
  * 
  */
 public class App {
 
-	/**
-	 * Program entry point
-	 * @param args command line args
-	 */
-	public static void main(String[] args) {
+  /**
+   * Program entry point
+   * 
+   * @param args command line args
+   */
+  public static void main(String[] args) {
 
-		Hero mage = new HeroBuilder(Profession.MAGE, "Riobard")
-				.withHairColor(HairColor.BLACK).withWeapon(Weapon.DAGGER)
-				.build();
-		System.out.println(mage);
+    Hero mage =
+        new HeroBuilder(Profession.MAGE, "Riobard").withHairColor(HairColor.BLACK)
+            .withWeapon(Weapon.DAGGER).build();
+    System.out.println(mage);
 
-		Hero warrior = new HeroBuilder(Profession.WARRIOR, "Amberjill")
-				.withHairColor(HairColor.BLOND)
-				.withHairType(HairType.LONG_CURLY).withArmor(Armor.CHAIN_MAIL)
-				.withWeapon(Weapon.SWORD).build();
-		System.out.println(warrior);
+    Hero warrior =
+        new HeroBuilder(Profession.WARRIOR, "Amberjill").withHairColor(HairColor.BLOND)
+            .withHairType(HairType.LONG_CURLY).withArmor(Armor.CHAIN_MAIL).withWeapon(Weapon.SWORD)
+            .build();
+    System.out.println(warrior);
 
-		Hero thief = new HeroBuilder(Profession.THIEF, "Desmond")
-				.withHairType(HairType.BALD).withWeapon(Weapon.BOW).build();
-		System.out.println(thief);
+    Hero thief =
+        new HeroBuilder(Profession.THIEF, "Desmond").withHairType(HairType.BALD)
+            .withWeapon(Weapon.BOW).build();
+    System.out.println(thief);
 
-	}
+  }
 }

builder/src/main/java/com/iluwatar/builder/Armor.java

@@ -7,16 +7,16 @@ package com.iluwatar.builder;
  */
 public enum Armor {
 
-	CLOTHES("clothes"), LEATHER("leather"), CHAIN_MAIL("chain mail"), PLATE_MAIL("plate mail");
+  CLOTHES("clothes"), LEATHER("leather"), CHAIN_MAIL("chain mail"), PLATE_MAIL("plate mail");
 
-    private String title;
+  private String title;
 
-    Armor(String title) {
-        this.title = title;
-    }
+  Armor(String title) {
+    this.title = title;
+  }
 
-    @Override
-	public String toString() {
-		return title;
-	}
+  @Override
+  public String toString() {
+    return title;
+  }
 }

builder/src/main/java/com/iluwatar/builder/HairColor.java

@@ -7,11 +7,11 @@ package com.iluwatar.builder;
  */
 public enum HairColor {
 
-	WHITE, BLOND, RED, BROWN, BLACK;
+  WHITE, BLOND, RED, BROWN, BLACK;
 
-	@Override
-	public String toString() {
-		return name().toLowerCase();
-	}
+  @Override
+  public String toString() {
+    return name().toLowerCase();
+  }
 
 }

builder/src/main/java/com/iluwatar/builder/HairType.java

@@ -7,16 +7,17 @@ package com.iluwatar.builder;
  */
 public enum HairType {
 
-	BALD("bald"), SHORT("short"), CURLY("curly"), LONG_STRAIGHT("long straight"), LONG_CURLY("long curly");
+  BALD("bald"), SHORT("short"), CURLY("curly"), LONG_STRAIGHT("long straight"), LONG_CURLY(
+      "long curly");
 
-    private String title;
+  private String title;
 
-    HairType(String title) {
-        this.title = title;
-    }
+  HairType(String title) {
+    this.title = title;
+  }
 
-    @Override
-	public String toString() {
-		return title;
-	}
+  @Override
+  public String toString() {
+    return title;
+  }
 }

builder/src/main/java/com/iluwatar/builder/Hero.java

@@ -7,123 +7,125 @@ package com.iluwatar.builder;
  */
 public class Hero {
 
-	private final Profession profession;
-	private final String name;
-	private final HairType hairType;
-	private final HairColor hairColor;
-	private final Armor armor;
-	private final Weapon weapon;
+  private final Profession profession;
+  private final String name;
+  private final HairType hairType;
+  private final HairColor hairColor;
+  private final Armor armor;
+  private final Weapon weapon;
 
-	public Profession getProfession() {
-		return profession;
-	}
+  public Profession getProfession() {
+    return profession;
+  }
 
-	public String getName() {
-		return name;
-	}
+  public String getName() {
+    return name;
+  }
 
-	public HairType getHairType() {
-		return hairType;
-	}
+  public HairType getHairType() {
+    return hairType;
+  }
 
-	public HairColor getHairColor() {
-		return hairColor;
-	}
+  public HairColor getHairColor() {
+    return hairColor;
+  }
 
-	public Armor getArmor() {
-		return armor;
-	}
+  public Armor getArmor() {
+    return armor;
+  }
 
-	public Weapon getWeapon() {
-		return weapon;
-	}
+  public Weapon getWeapon() {
+    return weapon;
+  }
 
-	@Override
-	public String toString() {
+  @Override
+  public String toString() {
 
-		StringBuilder sb = new StringBuilder();
-		sb.append("This is a ");
-		sb.append(profession);
-		sb.append(" named ");
-		sb.append(name);
-		if (hairColor != null || hairType != null) {
-			sb.append(" with ");
-			if (hairColor != null) {
-				sb.append(hairColor);
-				sb.append(" ");
-			}
-			if (hairType != null) {
-				sb.append(hairType);
-				sb.append(" ");
-			}
-			sb.append(hairType != HairType.BALD ? "hair" : "head");
-		}
-		if (armor != null) {
-			sb.append(" wearing ");
-			sb.append(armor);
-		}
-		if (weapon != null) {
-			sb.append(" and wielding a ");
-			sb.append(weapon);
-		}
-		sb.append(".");
-		return sb.toString();
-	}
+    StringBuilder sb = new StringBuilder();
+    sb.append("This is a ");
+    sb.append(profession);
+    sb.append(" named ");
+    sb.append(name);
+    if (hairColor != null || hairType != null) {
+      sb.append(" with ");
+      if (hairColor != null) {
+        sb.append(hairColor);
+        sb.append(" ");
+      }
+      if (hairType != null) {
+        sb.append(hairType);
+        sb.append(" ");
+      }
+      sb.append(hairType != HairType.BALD ? "hair" : "head");
+    }
+    if (armor != null) {
+      sb.append(" wearing ");
+      sb.append(armor);
+    }
+    if (weapon != null) {
+      sb.append(" and wielding a ");
+      sb.append(weapon);
+    }
+    sb.append(".");
+    return sb.toString();
+  }
 
-	private Hero(HeroBuilder builder) {
-		this.profession = builder.profession;
-		this.name = builder.name;
-		this.hairColor = builder.hairColor;
-		this.hairType = builder.hairType;
-		this.weapon = builder.weapon;
-		this.armor = builder.armor;
-	}
+  private Hero(HeroBuilder builder) {
+    this.profession = builder.profession;
+    this.name = builder.name;
+    this.hairColor = builder.hairColor;
+    this.hairType = builder.hairType;
+    this.weapon = builder.weapon;
+    this.armor = builder.armor;
+  }
 
-	/**
-	 * 
-	 * The builder class.
-	 * 
-	 */
-	public static class HeroBuilder {
+  /**
+   * 
+   * The builder class.
+   * 
+   */
+  public static class HeroBuilder {
 
-		private final Profession profession;
-		private final String name;
-		private HairType hairType;
-		private HairColor hairColor;
-		private Armor armor;
-		private Weapon weapon;
+    private final Profession profession;
+    private final String name;
+    private HairType hairType;
+    private HairColor hairColor;
+    private Armor armor;
+    private Weapon weapon;
 
-		public HeroBuilder(Profession profession, String name) {
-			if (profession == null || name == null) {
-				throw new IllegalArgumentException(
-						"profession and name can not be null");
-			}
-			this.profession = profession;
-			this.name = name;
-		}
+    /**
+     * Constructor
+     */
+    public HeroBuilder(Profession profession, String name) {
+      if (profession == null || name == null) {
+        throw new IllegalArgumentException("profession and name can not be null");
+      }
+      this.profession = profession;
+      this.name = name;
+    }
 
-		public HeroBuilder withHairType(HairType hairType) {
-			this.hairType = hairType;
-			return this;
-		}
+    public HeroBuilder withHairType(HairType hairType) {
+      this.hairType = hairType;
+      return this;
+    }
 
-		public HeroBuilder withHairColor(HairColor hairColor) {
-			this.hairColor = hairColor;
-			return this;
-		}
+    public HeroBuilder withHairColor(HairColor hairColor) {
+      this.hairColor = hairColor;
+      return this;
+    }
 
-		public HeroBuilder withArmor(Armor armor) {
-			this.armor = armor;
-			return this;
-		}
+    public HeroBuilder withArmor(Armor armor) {
+      this.armor = armor;
+      return this;
+    }
 
-		public HeroBuilder withWeapon(Weapon weapon) {
-			this.weapon = weapon;
-			return this;
-		}
+    public HeroBuilder withWeapon(Weapon weapon) {
+      this.weapon = weapon;
+      return this;
+    }
 
-		public Hero build() {
-			return new Hero(this);
-		}
-	}
+    public Hero build() {
+      return new Hero(this);
+    }
+  }
 }

builder/src/main/java/com/iluwatar/builder/Profession.java

@@ -7,11 +7,10 @@ package com.iluwatar.builder;
  */
 public enum Profession {
 
-	WARRIOR, THIEF, MAGE, PRIEST;
-
-	@Override
-	public String toString() {
-		return name().toLowerCase();
-	}
+  WARRIOR, THIEF, MAGE, PRIEST;
 
+  @Override
+  public String toString() {
+    return name().toLowerCase();
+  }
 }

builder/src/main/java/com/iluwatar/builder/Weapon.java

@@ -7,11 +7,10 @@ package com.iluwatar.builder;
  */
 public enum Weapon {
 
-	DAGGER, SWORD, AXE, WARHAMMER, BOW;
-
-	@Override
-	public String toString() {
-		return name().toLowerCase();
-	}
+  DAGGER, SWORD, AXE, WARHAMMER, BOW;
 
+  @Override
+  public String toString() {
+    return name().toLowerCase();
+  }
 }

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

@@ -2,8 +2,6 @@ package com.iluwatar.builder;
 
 import org.junit.Test;
 
-import com.iluwatar. builder.App;
-
 /**
  * 
  * Application test
@@ -11,9 +9,9 @@ import com.iluwatar. builder.App;
  */
 public class AppTest {
 
-	@Test
-	public void test() {
-		String[] args = {};
-		App.main(args);
-	}
+  @Test
+  public void test() {
+    String[] args = {};
+    App.main(args);
+  }
 }

builder/src/test/java/com/iluwatar/builder/HeroTest.java

@@ -0,0 +1,56 @@
+package com.iluwatar.builder;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+/**
+ * Date: 12/6/15 - 11:01 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class HeroTest {
+
+  /**
+   * Test if we get the expected exception when trying to create a hero without a profession
+   */
+  @Test(expected = IllegalArgumentException.class)
+  public void testMissingProfession() throws Exception {
+    new Hero.HeroBuilder(null, "Sir without a job");
+  }
+
+  /**
+   * Test if we get the expected exception when trying to create a hero without a name
+   */
+  @Test(expected = IllegalArgumentException.class)
+  public void testMissingName() throws Exception {
+    new Hero.HeroBuilder(Profession.THIEF, null);
+  }
+
+  /**
+   * Test if the hero build by the builder has the correct attributes, as requested
+   */
+  @Test
+  public void testBuildHero() throws Exception {
+    final String heroName = "Sir Lancelot";
+
+    final Hero hero = new Hero.HeroBuilder(Profession.WARRIOR, heroName)
+        .withArmor(Armor.CHAIN_MAIL)
+        .withWeapon(Weapon.SWORD)
+        .withHairType(HairType.LONG_CURLY)
+        .withHairColor(HairColor.BLOND)
+        .build();
+
+    assertNotNull(hero);
+    assertNotNull(hero.toString());
+    assertEquals(Profession.WARRIOR, hero.getProfession());
+    assertEquals(heroName, hero.getName());
+    assertEquals(Armor.CHAIN_MAIL, hero.getArmor());
+    assertEquals(Weapon.SWORD, hero.getWeapon());
+    assertEquals(HairType.LONG_CURLY, hero.getHairType());
+    assertEquals(HairColor.BLOND, hero.getHairColor());
+
+  }
+
+}

business-delegate/index.md

@@ -4,7 +4,9 @@ title: Business Delegate
 folder: business-delegate
 permalink: /patterns/business-delegate/
 categories: Business Tier
-tags: Java
+tags:
+ - Java
+ - Difficulty-Intermediate
 ---
 
 **Intent:** The Business Delegate pattern adds an abstraction layer between

business-delegate/pom.xml

@@ -6,7 +6,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.7.0</version>
+		<version>1.9.0</version>
 	</parent>
 	<artifactId>business-delegate</artifactId>
 	<dependencies>
@@ -15,5 +15,10 @@
 			<artifactId>junit</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.mockito</groupId>
+			<artifactId>mockito-core</artifactId>
+			<scope>test</scope>
+		</dependency>
 	</dependencies>
 </project>

business-delegate/src/main/java/com/iluwatar/business/delegate/App.java

@@ -1,35 +1,40 @@
 package com.iluwatar.business.delegate;
 
 /**
+ * The Business Delegate pattern adds an abstraction layer between the presentation and business
+ * tiers. By using the pattern we gain loose coupling between the tiers. The Business Delegate
+ * encapsulates knowledge about how to locate, connect to, and interact with the business objects
+ * that make up the application.
  * 
- * The Business Delegate pattern adds an abstraction layer between the presentation and business tiers.
- * By using the pattern we gain loose coupling between the tiers. The Business Delegate encapsulates
- * knowledge about how to locate, connect to, and interact with the business objects that make up
- * the application.
- * <p>
- * Some of the services the Business Delegate uses are instantiated directly, and some can be retrieved
- * through service lookups. The Business Delegate itself may contain business logic too potentially tying
- * together multiple service calls, exception handling, retrying etc.
- * <p>
- * In this example the client ({@link Client}) utilizes a business delegate ({@link BusinessDelegate}) to execute a task.
- * The Business Delegate then selects the appropriate service and makes the service call.
- *
+ * <p>Some of the services the Business Delegate uses are instantiated directly, and some can be
+ * retrieved through service lookups. The Business Delegate itself may contain business logic too
+ * potentially tying together multiple service calls, exception handling, retrying etc.
+ * 
+ * <p>In this example the client ({@link Client}) utilizes a business delegate (
+ * {@link BusinessDelegate}) to execute a task. The Business Delegate then selects the appropriate
+ * service and makes the service call.
  */
 public class App {
-	
-	/**
-	 * Program entry point
-	 * @param args command line args
-	 */
-	public static void main(String[] args) {
-		
-		BusinessDelegate businessDelegate = new BusinessDelegate();
-		businessDelegate.setServiceType(ServiceType.EJB);
 
-		Client client = new Client(businessDelegate);
-		client.doTask();
+  /**
+   * Program entry point.
+   *
+   * @param args command line args
+   */
+  public static void main(String[] args) {
 
-		businessDelegate.setServiceType(ServiceType.JMS);
-		client.doTask();
-	}
+    BusinessDelegate businessDelegate = new BusinessDelegate();
+    BusinessLookup businessLookup = new BusinessLookup();
+    businessLookup.setEjbService(new EjbService());
+    businessLookup.setJmsService(new JmsService());
+
+    businessDelegate.setLookupService(businessLookup);
+    businessDelegate.setServiceType(ServiceType.EJB);
+
+    Client client = new Client(businessDelegate);
+    client.doTask();
+
+    businessDelegate.setServiceType(ServiceType.JMS);
+    client.doTask();
+  }
 }

business-delegate/src/main/java/com/iluwatar/business/delegate/BusinessDelegate.java

@@ -1,22 +1,24 @@
 package com.iluwatar.business.delegate;
 
 /**
- * 
  * BusinessDelegate separates the presentation and business tiers
- *
  */
 public class BusinessDelegate {
-	
-	private BusinessLookup lookupService = new BusinessLookup();
-	private BusinessService businessService;
-	private ServiceType serviceType;
 
-	public void setServiceType(ServiceType serviceType) {
-		this.serviceType = serviceType;
-	}
+  private BusinessLookup lookupService;
+  private BusinessService businessService;
+  private ServiceType serviceType;
 
-	public void doTask() {
-		businessService = lookupService.getBusinessService(serviceType);
-		businessService.doProcessing();
-	}
+  public void setLookupService(BusinessLookup businessLookup) {
+    this.lookupService = businessLookup;
+  }
+
+  public void setServiceType(ServiceType serviceType) {
+    this.serviceType = serviceType;
+  }
+
+  public void doTask() {
+    businessService = lookupService.getBusinessService(serviceType);
+    businessService.doProcessing();
+  }
 }

business-delegate/src/main/java/com/iluwatar/business/delegate/BusinessLookup.java

@@ -1,17 +1,31 @@
 package com.iluwatar.business.delegate;
 
 /**
- * 
- * Class for performing service lookups
- *
+ * Class for performing service lookups.
  */
 public class BusinessLookup {
 
-	public BusinessService getBusinessService(ServiceType serviceType) {
-		if (serviceType.equals(ServiceType.EJB)) {
-			return new EjbService();
-		} else {
-			return new JmsService();
-		}
-	}
+  private EjbService ejbService;
+
+  private JmsService jmsService;
+
+  /**
+   * @param serviceType Type of service instance to be returned.
+   * @return Service instance.
+   */
+  public BusinessService getBusinessService(ServiceType serviceType) {
+    if (serviceType.equals(ServiceType.EJB)) {
+      return ejbService;
+    } else {
+      return jmsService;
+    }
+  }
+
+  public void setJmsService(JmsService jmsService) {
+    this.jmsService = jmsService;
+  }
+
+  public void setEjbService(EjbService ejbService) {
+    this.ejbService = ejbService;
+  }
 }

business-delegate/src/main/java/com/iluwatar/business/delegate/BusinessService.java

@@ -7,5 +7,5 @@ package com.iluwatar.business.delegate;
  */
 public interface BusinessService {
 
-	void doProcessing();
+  void doProcessing();
 }

business-delegate/src/main/java/com/iluwatar/business/delegate/Client.java

@@ -7,13 +7,13 @@ package com.iluwatar.business.delegate;
  */
 public class Client {
 
-	private BusinessDelegate businessDelegate;
+  private BusinessDelegate businessDelegate;
 
-	public Client(BusinessDelegate businessDelegate) {
-		this.businessDelegate = businessDelegate;
-	}
+  public Client(BusinessDelegate businessDelegate) {
+    this.businessDelegate = businessDelegate;
+  }
 
-	public void doTask() {
-		businessDelegate.doTask();
-	}
+  public void doTask() {
+    businessDelegate.doTask();
+  }
 }

business-delegate/src/main/java/com/iluwatar/business/delegate/EjbService.java

@@ -7,8 +7,8 @@ package com.iluwatar.business.delegate;
  */
 public class EjbService implements BusinessService {
 
-	@Override
-	public void doProcessing() {
-		System.out.println("EjbService is now processing");
-	}
+  @Override
+  public void doProcessing() {
+    System.out.println("EjbService is now processing");
+  }
 }

business-delegate/src/main/java/com/iluwatar/business/delegate/JmsService.java

@@ -7,8 +7,8 @@ package com.iluwatar.business.delegate;
  */
 public class JmsService implements BusinessService {
 
-	@Override
-	public void doProcessing() {
-		System.out.println("JmsService is now processing");
-	}
+  @Override
+  public void doProcessing() {
+    System.out.println("JmsService is now processing");
+  }
 }

business-delegate/src/main/java/com/iluwatar/business/delegate/ServiceType.java

@@ -6,6 +6,6 @@ package com.iluwatar.business.delegate;
  *
  */
 public enum ServiceType {
-	
-	EJB, JMS;
+
+  EJB, JMS;
 }

business-delegate/src/test/java/com/iluwatar/business/delegate/AppTest.java

@@ -1,19 +0,0 @@
-package com.iluwatar.business.delegate;
-
-import org.junit.Test;
-
-import com.iluwatar.business.delegate.App;
-
-/**
- * 
- * Application test
- *
- */
-public class AppTest {
-	
-	@Test
-	public void test() {
-		String[] args = {};
-		App.main(args);
-	}
-}

business-delegate/src/test/java/com/iluwatar/business/delegate/BusinessDelegateTest.java

@@ -0,0 +1,78 @@
+package com.iluwatar.business.delegate;
+
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * The Business Delegate pattern adds an abstraction layer between the presentation and business
+ * tiers. By using the pattern we gain loose coupling between the tiers. The Business Delegate
+ * encapsulates knowledge about how to locate, connect to, and interact with the business objects
+ * that make up the application.
+ * 
+ * <p>Some of the services the Business Delegate uses are instantiated directly, and some can be
+ * retrieved through service lookups. The Business Delegate itself may contain business logic too
+ * potentially tying together multiple service calls, exception handling, retrying etc.
+ */
+public class BusinessDelegateTest {
+
+  private EjbService ejbService;
+
+  private JmsService jmsService;
+
+  private BusinessLookup businessLookup;
+
+  private BusinessDelegate businessDelegate;
+
+  /**
+   * This method sets up the instance variables of this test class. It is executed before the
+   * execution of every test.
+   */
+  @Before
+  public void setup() {
+    ejbService = spy(new EjbService());
+    jmsService = spy(new JmsService());
+
+    businessLookup = spy(new BusinessLookup());
+    businessLookup.setEjbService(ejbService);
+    businessLookup.setJmsService(jmsService);
+
+    businessDelegate = spy(new BusinessDelegate());
+    businessDelegate.setLookupService(businessLookup);
+  }
+
+  /**
+   * In this example the client ({@link Client}) utilizes a business delegate (
+   * {@link BusinessDelegate}) to execute a task. The Business Delegate then selects the appropriate
+   * service and makes the service call.
+   */
+  @Test
+  public void testBusinessDelegate() {
+
+    // setup a client object
+    Client client = new Client(businessDelegate);
+
+    // set the service type
+    businessDelegate.setServiceType(ServiceType.EJB);
+
+    // action
+    client.doTask();
+
+    // verifying that the businessDelegate was used by client during doTask() method.
+    verify(businessDelegate).doTask();
+    verify(ejbService).doProcessing();
+
+    // set the service type
+    businessDelegate.setServiceType(ServiceType.JMS);
+
+    // action
+    client.doTask();
+
+    // verifying that the businessDelegate was used by client during doTask() method.
+    verify(businessDelegate, times(2)).doTask();
+    verify(jmsService).doProcessing();
+  }
+}

caching/index.md

@@ -6,6 +6,8 @@ permalink: /patterns/caching/
 categories: Other
 tags:
  - Java
+ - Difficulty-Intermediate
+ - Performance
 ---
 
 **Intent:** To avoid expensive re-acquisition of resources by not releasing

caching/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.7.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>caching</artifactId>
   <dependencies>

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

@@ -21,7 +21,7 @@ package com.iluwatar.caching;
  * application data. The cache itself is implemented as an internal (Java) data structure. It adopts
  * a Least-Recently-Used (LRU) strategy for evicting data from itself when its full. The three
  * strategies are individually tested. The testing of the cache is restricted towards saving and
- * querying of user accounts from the underlying data store ( {@link DBManager}). The main class (
+ * querying of user accounts from the underlying data store ( {@link DbManager}). The main class (
  * {@link App} is not aware of the underlying mechanics of the application (i.e. save and query) and
  * whether the data is coming from the cache or the DB (i.e. separation of concern). The AppManager
  * ({@link AppManager}) handles the transaction of data to-and-from the underlying data store
@@ -43,7 +43,7 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    AppManager.initDB(false); // VirtualDB (instead of MongoDB) was used in running the JUnit tests
+    AppManager.initDb(false); // VirtualDB (instead of MongoDB) was used in running the JUnit tests
                               // and the App class to avoid Maven compilation errors. Set flag to
                               // true to run the tests with MongoDB (provided that MongoDB is
                               // installed and socket connection is open).
@@ -65,8 +65,8 @@ public class App {
 
     AppManager.save(userAccount1);
     System.out.println(AppManager.printCacheContent());
-    userAccount1 = AppManager.find("001");
-    userAccount1 = AppManager.find("001");
+    AppManager.find("001");
+    AppManager.find("001");
   }
 
   /**
@@ -80,15 +80,15 @@ public class App {
 
     AppManager.save(userAccount2);
     System.out.println(AppManager.printCacheContent());
-    userAccount2 = AppManager.find("002");
+    AppManager.find("002");
     System.out.println(AppManager.printCacheContent());
     userAccount2 = AppManager.find("002");
     userAccount2.setUserName("Jane G.");
     AppManager.save(userAccount2);
     System.out.println(AppManager.printCacheContent());
-    userAccount2 = AppManager.find("002");
+    AppManager.find("002");
     System.out.println(AppManager.printCacheContent());
-    userAccount2 = AppManager.find("002");
+    AppManager.find("002");
   }
 
   /**
@@ -106,12 +106,12 @@ public class App {
     AppManager.save(userAccount4);
     AppManager.save(userAccount5);
     System.out.println(AppManager.printCacheContent());
-    userAccount3 = AppManager.find("003");
+    AppManager.find("003");
     System.out.println(AppManager.printCacheContent());
     UserAccount userAccount6 = new UserAccount("006", "Yasha", "She is an only child.");
     AppManager.save(userAccount6);
     System.out.println(AppManager.printCacheContent());
-    userAccount4 = AppManager.find("004");
+    AppManager.find("004");
     System.out.println(AppManager.printCacheContent());
   }
 }

caching/src/main/java/com/iluwatar/caching/AppManager.java

@@ -15,24 +15,30 @@ public class AppManager {
 
   private static CachingPolicy cachingPolicy;
 
+  private AppManager() {
+  }
+
   /**
    *
    * Developer/Tester is able to choose whether the application should use MongoDB as its underlying
    * data storage or a simple Java data structure to (temporarily) store the data/objects during
    * runtime.
    */
-  public static void initDB(boolean useMongoDB) {
-    if (useMongoDB) {
+  public static void initDb(boolean useMongoDb) {
+    if (useMongoDb) {
       try {
-        DBManager.connect();
+        DbManager.connect();
       } catch (ParseException e) {
         e.printStackTrace();
       }
     } else {
-      DBManager.createVirtualDB();
+      DbManager.createVirtualDb();
     }
   }
 
+  /**
+   * Initialize caching policy
+   */
   public static void initCachingPolicy(CachingPolicy policy) {
     cachingPolicy = policy;
     if (cachingPolicy == CachingPolicy.BEHIND) {
@@ -50,15 +56,21 @@ public class AppManager {
     CacheStore.initCapacity(capacity);
   }
 
-  public static UserAccount find(String userID) {
+  /**
+   * Find user account
+   */
+  public static UserAccount find(String userId) {
     if (cachingPolicy == CachingPolicy.THROUGH || cachingPolicy == CachingPolicy.AROUND) {
-      return CacheStore.readThrough(userID);
+      return CacheStore.readThrough(userId);
     } else if (cachingPolicy == CachingPolicy.BEHIND) {
-      return CacheStore.readThroughWithWriteBackPolicy(userID);
+      return CacheStore.readThroughWithWriteBackPolicy(userId);
     }
     return null;
   }
 
+  /**
+   * Save user account
+   */
   public static void save(UserAccount userAccount) {
     if (cachingPolicy == CachingPolicy.THROUGH) {
       CacheStore.writeThrough(userAccount);

caching/src/main/java/com/iluwatar/caching/CacheStore.java

@@ -9,73 +9,99 @@ import java.util.ArrayList;
  */
 public class CacheStore {
 
-  static LRUCache cache = null;
+  static LruCache cache = null;
 
-  public static void initCapacity(int capacity) {
-    if (null == cache)
-      cache = new LRUCache(capacity);
-    else
-      cache.setCapacity(capacity);
+  private CacheStore() {
   }
 
-  public static UserAccount readThrough(String userID) {
-    if (cache.contains(userID)) {
+  /**
+   * Init cache capacity
+   */
+  public static void initCapacity(int capacity) {
+    if (null == cache) {
+      cache = new LruCache(capacity);
+    } else {
+      cache.setCapacity(capacity);
+    }
+  }
+
+  /**
+   * Get user account using read-through cache
+   */
+  public static UserAccount readThrough(String userId) {
+    if (cache.contains(userId)) {
       System.out.println("# Cache Hit!");
-      return cache.get(userID);
+      return cache.get(userId);
     }
     System.out.println("# Cache Miss!");
-    UserAccount userAccount = DBManager.readFromDB(userID);
-    cache.set(userID, userAccount);
+    UserAccount userAccount = DbManager.readFromDb(userId);
+    cache.set(userId, userAccount);
     return userAccount;
   }
 
+  /**
+   * Get user account using write-through cache
+   */
   public static void writeThrough(UserAccount userAccount) {
-    if (cache.contains(userAccount.getUserID())) {
-      DBManager.updateDB(userAccount);
+    if (cache.contains(userAccount.getUserId())) {
+      DbManager.updateDb(userAccount);
     } else {
-      DBManager.writeToDB(userAccount);
+      DbManager.writeToDb(userAccount);
     }
-    cache.set(userAccount.getUserID(), userAccount);
+    cache.set(userAccount.getUserId(), userAccount);
   }
 
+  /**
+   * Get user account using write-around cache
+   */
   public static void writeAround(UserAccount userAccount) {
-    if (cache.contains(userAccount.getUserID())) {
-      DBManager.updateDB(userAccount);
-      cache.invalidate(userAccount.getUserID()); // Cache data has been updated -- remove older
+    if (cache.contains(userAccount.getUserId())) {
+      DbManager.updateDb(userAccount);
+      cache.invalidate(userAccount.getUserId()); // Cache data has been updated -- remove older
                                                  // version from cache.
     } else {
-      DBManager.writeToDB(userAccount);
+      DbManager.writeToDb(userAccount);
     }
   }
 
-  public static UserAccount readThroughWithWriteBackPolicy(String userID) {
-    if (cache.contains(userID)) {
+  /**
+   * Get user account using read-through cache with write-back policy
+   */
+  public static UserAccount readThroughWithWriteBackPolicy(String userId) {
+    if (cache.contains(userId)) {
       System.out.println("# Cache Hit!");
-      return cache.get(userID);
+      return cache.get(userId);
     }
     System.out.println("# Cache Miss!");
-    UserAccount userAccount = DBManager.readFromDB(userID);
+    UserAccount userAccount = DbManager.readFromDb(userId);
     if (cache.isFull()) {
       System.out.println("# Cache is FULL! Writing LRU data to DB...");
-      UserAccount toBeWrittenToDB = cache.getLRUData();
-      DBManager.upsertDB(toBeWrittenToDB);
+      UserAccount toBeWrittenToDb = cache.getLruData();
+      DbManager.upsertDb(toBeWrittenToDb);
     }
-    cache.set(userID, userAccount);
+    cache.set(userId, userAccount);
     return userAccount;
   }
 
+  /**
+   * Set user account
+   */
   public static void writeBehind(UserAccount userAccount) {
-    if (cache.isFull() && !cache.contains(userAccount.getUserID())) {
+    if (cache.isFull() && !cache.contains(userAccount.getUserId())) {
       System.out.println("# Cache is FULL! Writing LRU data to DB...");
-      UserAccount toBeWrittenToDB = cache.getLRUData();
-      DBManager.upsertDB(toBeWrittenToDB);
+      UserAccount toBeWrittenToDb = cache.getLruData();
+      DbManager.upsertDb(toBeWrittenToDb);
     }
-    cache.set(userAccount.getUserID(), userAccount);
+    cache.set(userAccount.getUserId(), userAccount);
   }
 
+  /**
+   * Clears cache
+   */
   public static void clearCache() {
-    if (null != cache)
+    if (null != cache) {
       cache.clear();
+    }
   }
 
   /**
@@ -83,14 +109,18 @@ public class CacheStore {
    */
   public static void flushCache() {
     System.out.println("# flushCache...");
-    if (null == cache)
+    if (null == cache) {
       return;
+    }
     ArrayList<UserAccount> listOfUserAccounts = cache.getCacheDataInListForm();
     for (UserAccount userAccount : listOfUserAccounts) {
-      DBManager.upsertDB(userAccount);
+      DbManager.upsertDb(userAccount);
     }
   }
 
+  /**
+   * Print user accounts
+   */
   public static String print() {
     ArrayList<UserAccount> listOfUserAccounts = cache.getCacheDataInListForm();
     StringBuilder sb = new StringBuilder();

caching/src/main/java/com/iluwatar/caching/DbManager.java

@@ -21,7 +21,7 @@ import com.mongodb.client.model.UpdateOptions;
  * during runtime (createVirtualDB()).</p>
  * 
  */
-public class DBManager {
+public class DbManager {
 
   private static MongoClient mongoClient;
   private static MongoDatabase db;
@@ -29,21 +29,34 @@ public class DBManager {
 
   private static HashMap<String, UserAccount> virtualDB;
 
-  public static void createVirtualDB() {
+  private DbManager() {
+  }
+
+  /**
+   * Create DB
+   */
+  public static void createVirtualDb() {
     useMongoDB = false;
     virtualDB = new HashMap<String, UserAccount>();
   }
 
+  /**
+   * Connect to DB
+   */
   public static void connect() throws ParseException {
     useMongoDB = true;
     mongoClient = new MongoClient();
     db = mongoClient.getDatabase("test");
   }
 
-  public static UserAccount readFromDB(String userID) {
+  /**
+   * Read user account from DB
+   */
+  public static UserAccount readFromDb(String userId) {
     if (!useMongoDB) {
-      if (virtualDB.containsKey(userID))
-        return virtualDB.get(userID);
+      if (virtualDB.containsKey(userId)) {
+        return virtualDB.get(userId);
+      }
       return null;
     }
     if (null == db) {
@@ -54,18 +67,22 @@ public class DBManager {
       }
     }
     FindIterable<Document> iterable =
-        db.getCollection("user_accounts").find(new Document("userID", userID));
-    if (iterable == null)
+        db.getCollection("user_accounts").find(new Document("userID", userId));
+    if (iterable == null) {
       return null;
+    }
     Document doc = iterable.first();
     UserAccount userAccount =
-        new UserAccount(userID, doc.getString("userName"), doc.getString("additionalInfo"));
+        new UserAccount(userId, doc.getString("userName"), doc.getString("additionalInfo"));
     return userAccount;
   }
 
-  public static void writeToDB(UserAccount userAccount) {
+  /**
+   * Write user account to DB
+   */
+  public static void writeToDb(UserAccount userAccount) {
     if (!useMongoDB) {
-      virtualDB.put(userAccount.getUserID(), userAccount);
+      virtualDB.put(userAccount.getUserId(), userAccount);
       return;
     }
     if (null == db) {
@@ -76,13 +93,16 @@ public class DBManager {
       }
     }
     db.getCollection("user_accounts").insertOne(
-        new Document("userID", userAccount.getUserID()).append("userName",
+        new Document("userID", userAccount.getUserId()).append("userName",
             userAccount.getUserName()).append("additionalInfo", userAccount.getAdditionalInfo()));
   }
 
-  public static void updateDB(UserAccount userAccount) {
+  /**
+   * Update DB
+   */
+  public static void updateDb(UserAccount userAccount) {
     if (!useMongoDB) {
-      virtualDB.put(userAccount.getUserID(), userAccount);
+      virtualDB.put(userAccount.getUserId(), userAccount);
       return;
     }
     if (null == db) {
@@ -93,7 +113,7 @@ public class DBManager {
       }
     }
     db.getCollection("user_accounts").updateOne(
-        new Document("userID", userAccount.getUserID()),
+        new Document("userID", userAccount.getUserId()),
         new Document("$set", new Document("userName", userAccount.getUserName()).append(
             "additionalInfo", userAccount.getAdditionalInfo())));
   }
@@ -102,9 +122,9 @@ public class DBManager {
    *
    * Insert data into DB if it does not exist. Else, update it.
    */
-  public static void upsertDB(UserAccount userAccount) {
+  public static void upsertDb(UserAccount userAccount) {
     if (!useMongoDB) {
-      virtualDB.put(userAccount.getUserID(), userAccount);
+      virtualDB.put(userAccount.getUserId(), userAccount);
       return;
     }
     if (null == db) {
@@ -115,8 +135,8 @@ public class DBManager {
       }
     }
     db.getCollection("user_accounts").updateOne(
-        new Document("userID", userAccount.getUserID()),
-        new Document("$set", new Document("userID", userAccount.getUserID()).append("userName",
+        new Document("userID", userAccount.getUserId()),
+        new Document("$set", new Document("userID", userAccount.getUserId()).append("userName",
             userAccount.getUserName()).append("additionalInfo", userAccount.getAdditionalInfo())),
         new UpdateOptions().upsert(true));
   }

caching/src/main/java/com/iluwatar/caching/LruCache.java

@@ -12,16 +12,16 @@ import java.util.HashMap;
  * LRU data is always at the end of the list.
  *
  */
-public class LRUCache {
+public class LruCache {
 
   class Node {
-    String userID;
+    String userId;
     UserAccount userAccount;
     Node previous;
     Node next;
 
-    public Node(String userID, UserAccount userAccount) {
-      this.userID = userID;
+    public Node(String userId, UserAccount userAccount) {
+      this.userId = userId;
       this.userAccount = userAccount;
     }
   }
@@ -31,13 +31,16 @@ public class LRUCache {
   Node head = null;
   Node end = null;
 
-  public LRUCache(int capacity) {
+  public LruCache(int capacity) {
     this.capacity = capacity;
   }
 
-  public UserAccount get(String userID) {
-    if (cache.containsKey(userID)) {
-      Node node = cache.get(userID);
+  /**
+   * Get user account
+   */
+  public UserAccount get(String userId) {
+    if (cache.containsKey(userId)) {
+      Node node = cache.get(userId);
       remove(node);
       setHead(node);
       return node.userAccount;
@@ -69,52 +72,63 @@ public class LRUCache {
   public void setHead(Node node) {
     node.next = head;
     node.previous = null;
-    if (head != null)
+    if (head != null) {
       head.previous = node;
+    }
     head = node;
-    if (end == null)
+    if (end == null) {
       end = head;
+    }
   }
 
-  public void set(String userID, UserAccount userAccount) {
-    if (cache.containsKey(userID)) {
-      Node old = cache.get(userID);
+  /**
+   * Set user account
+   */
+  public void set(String userId, UserAccount userAccount) {
+    if (cache.containsKey(userId)) {
+      Node old = cache.get(userId);
       old.userAccount = userAccount;
       remove(old);
       setHead(old);
     } else {
-      Node newNode = new Node(userID, userAccount);
+      Node newNode = new Node(userId, userAccount);
       if (cache.size() >= capacity) {
-        System.out.println("# Cache is FULL! Removing " + end.userID + " from cache...");
-        cache.remove(end.userID); // remove LRU data from cache.
+        System.out.println("# Cache is FULL! Removing " + end.userId + " from cache...");
+        cache.remove(end.userId); // remove LRU data from cache.
         remove(end);
         setHead(newNode);
       } else {
         setHead(newNode);
       }
-      cache.put(userID, newNode);
+      cache.put(userId, newNode);
     }
   }
 
-  public boolean contains(String userID) {
-    return cache.containsKey(userID);
+  public boolean contains(String userId) {
+    return cache.containsKey(userId);
   }
 
-  public void invalidate(String userID) {
-    System.out.println("# " + userID + " has been updated! Removing older version from cache...");
-    Node toBeRemoved = cache.get(userID);
+  /**
+   * Invalidate cache for user
+   */
+  public void invalidate(String userId) {
+    System.out.println("# " + userId + " has been updated! Removing older version from cache...");
+    Node toBeRemoved = cache.get(userId);
     remove(toBeRemoved);
-    cache.remove(userID);
+    cache.remove(userId);
   }
 
   public boolean isFull() {
     return cache.size() >= capacity;
   }
 
-  public UserAccount getLRUData() {
+  public UserAccount getLruData() {
     return end.userAccount;
   }
 
+  /**
+   * Clear cache
+   */
   public void clear() {
     head = null;
     end = null;
@@ -135,6 +149,9 @@ public class LRUCache {
     return listOfCacheData;
   }
 
+  /**
+   * Set cache capacity
+   */
   public void setCapacity(int newCapacity) {
     if (capacity > newCapacity) {
       clear(); // Behavior can be modified to accommodate for decrease in cache size. For now, we'll

caching/src/main/java/com/iluwatar/caching/UserAccount.java

@@ -6,22 +6,25 @@ package com.iluwatar.caching;
  *
  */
 public class UserAccount {
-  private String userID;
+  private String userId;
   private String userName;
   private String additionalInfo;
 
-  public UserAccount(String userID, String userName, String additionalInfo) {
-    this.userID = userID;
+  /**
+   * Constructor
+   */
+  public UserAccount(String userId, String userName, String additionalInfo) {
+    this.userId = userId;
     this.userName = userName;
     this.additionalInfo = additionalInfo;
   }
 
-  public String getUserID() {
-    return userID;
+  public String getUserId() {
+    return userId;
   }
 
-  public void setUserID(String userID) {
-    this.userID = userID;
+  public void setUserId(String userId) {
+    this.userId = userId;
   }
 
   public String getUserName() {
@@ -42,6 +45,6 @@ public class UserAccount {
 
   @Override
   public String toString() {
-    return userID + ", " + userName + ", " + additionalInfo;
+    return userId + ", " + userName + ", " + additionalInfo;
   }
 }

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

@@ -16,7 +16,7 @@ public class AppTest {
    */
   @Before
   public void setUp() {
-    AppManager.initDB(false); // VirtualDB (instead of MongoDB) was used in running the JUnit tests
+    AppManager.initDb(false); // VirtualDB (instead of MongoDB) was used in running the JUnit tests
                               // to avoid Maven compilation errors. Set flag to true to run the
                               // tests with MongoDB (provided that MongoDB is installed and socket
                               // connection is open).

callback/index.md

@@ -4,7 +4,11 @@ title: Callback
 folder: callback
 permalink: /patterns/callback/
 categories: Other
-tags: Java
+tags:
+ - Java
+ - Difficulty-Beginner
+ - Functional
+ - Idiom
 ---
 
 **Intent:** Callback is a piece of executable code that is passed as an

callback/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.7.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>callback</artifactId>
   <dependencies>

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

@@ -2,20 +2,24 @@ package com.iluwatar.callback;
 
 /**
  * 
- * Callback pattern is more native for functional languages where functions are treated as first-class citizens.
- * Prior to Java 8 callbacks can be simulated using simple (alike command) interfaces.
+ * Callback pattern is more native for functional languages where functions are treated as
+ * first-class citizens. Prior to Java 8 callbacks can be simulated using simple (alike command)
+ * interfaces.
  * 
  */
 public class App {
 
-	public static void main(String[] args) {
-		Task task = new SimpleTask();
-		Callback callback = new Callback() {
-			@Override
-			public void call() {
-				System.out.println("I'm done now.");
-			}
-		};
-		task.executeWith(callback);
-	}
+  /**
+   * Program entry point
+   */
+  public static void main(String[] args) {
+    Task task = new SimpleTask();
+    Callback callback = new Callback() {
+      @Override
+      public void call() {
+        System.out.println("I'm done now.");
+      }
+    };
+    task.executeWith(callback);
+  }
 }

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

@@ -7,5 +7,5 @@ package com.iluwatar.callback;
  */
 public interface Callback {
 
-	public void call();
+  void call();
 }

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

@@ -7,9 +7,8 @@ package com.iluwatar.callback;
  */
 public class SimpleTask extends Task {
 
-	@Override
-	public void execute() {
-		System.out.println("Perform some important activity and after call the callback method.");
-	}
-
+  @Override
+  public void execute() {
+    System.out.println("Perform some important activity and after call the callback method.");
+  }
 }