Set version number for monthly release

Fix #216 Repository vs DAO

.travis.yml

@@ -1,20 +1,18 @@
 language: java
-
 jdk:
-  - oraclejdk8
+- oraclejdk8
 
 env:
   global:
   - GH_REF: github.com/iluwatar/java-design-patterns.git
-  - secure: "LxTDuNS/rBWIvKkaEqr79ImZAe48mCdoYCF41coxNXgNoippo4GIBArknqtv+XvdkiuRZ1yGyj6pn8GU33c/yn+krddTUkVCwTbVatbalW5jhQjDbHYym/JcxaK9ZS/3JTeGcWrBgiPqHEEDhCf26vPZsXoMSeVCEORVKTp1BSg="
-
-before_install:
-  - "export DISPLAY=:99.0"
-  - "sh -e /etc/init.d/xvfb start"
+  - secure: LxTDuNS/rBWIvKkaEqr79ImZAe48mCdoYCF41coxNXgNoippo4GIBArknqtv+XvdkiuRZ1yGyj6pn8GU33c/yn+krddTUkVCwTbVatbalW5jhQjDbHYym/JcxaK9ZS/3JTeGcWrBgiPqHEEDhCf26vPZsXoMSeVCEORVKTp1BSg=
   
-after_success:
-  - mvn clean test jacoco:report coveralls:report
-  - bash update-ghpages.sh
+before_install:
+- export DISPLAY=:99.0
+- sh -e /etc/init.d/xvfb start
+
+after_success:
+- mvn clean test jacoco:report coveralls:report
+- bash update-ghpages.sh
 
-# Migration to container-based infrastructure  
 sudo: false

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 
+
+

README.md

@@ -23,10 +23,16 @@ are familiar with the patterns.
 
 # Getting started
 
-Before you dive into the material, you should be familiar with various 
-[Programming/Software Design Principles](http://webpro.github.io/programming-principles/). 
+Before you dive into the material, you should be familiar with various
+[Programming/Software Design Principles](http://webpro.github.io/programming-principles/).
 
-Once you are familiar with these concepts you can start drilling down into patterns by any of the following approaches
+All designs should be as simple as possible. You should start with KISS, YAGNI,
+and Do The Simplest Thing That Could Possibly Work principles. Complexity and
+patterns should only be introduced when they are needed for practical
+extensibility.
+
+Once you are familiar with these concepts you can start drilling down into
+patterns by any of the following approaches
 
  - Using difficulty tags, `Difficulty-Beginner`, `Difficulty-Intermediate` & `Difficulty-Expert`.
  - Using pattern categories, `Creational`, `Behavioral` and others.
@@ -38,7 +44,6 @@ If you are willing to contribute to the project you will find the relevant infor
 
 # Credits
 
-* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
 * [Effective Java (2nd Edition)](http://www.amazon.com/Effective-Java-Edition-Joshua-Bloch/dp/0321356683)
 * [Java Generics and Collections](http://www.amazon.com/Java-Generics-Collections-Maurice-Naftalin/dp/0596527756/)
 * [Let's Modify the Objects-First Approach into Design-Patterns-First](http://edu.pecinovsky.cz/papers/2006_ITiCSE_Design_Patterns_First.pdf)
@@ -48,7 +53,6 @@ If you are willing to contribute to the project you will find the relevant infor
 * [Patterns of Enterprise Application Architecture](http://www.amazon.com/Patterns-Enterprise-Application-Architecture-Martin/dp/0321127420)
 * [Spring Data](http://www.amazon.com/Spring-Data-Mark-Pollack/dp/1449323952/ref=sr_1_1)
 * [J2EE Design Patterns](http://www.amazon.com/J2EE-Design-Patterns-William-Crawford/dp/0596004273/ref=sr_1_2)
-* [Pattern Oriented Software Architecture Vol I-V](http://www.amazon.com/Pattern-Oriented-Software-Architecture-Volume-Patterns/dp/0471958697)
 
 # License
 

abstract-factory/index.md

@@ -4,9 +4,13 @@ title: Abstract Factory
 folder: abstract-factory
 permalink: /patterns/abstract-factory/
 categories: Creational
-tags: Java
+tags: 
+ - Java
+ - Gang Of Four
 ---
 
+**Also known as:** Kit
+
 **Intent:** Provide an interface for creating families of related or dependent
 objects without specifying their concrete classes.
 
@@ -22,3 +26,7 @@ objects without specifying their concrete classes.
 **Real world examples:**
 
 * [javax.xml.parsers.DocumentBuilderFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/parsers/DocumentBuilderFactory.html)
+
+**Credits**
+
+* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)

abstract-factory/pom.xml

@@ -1,19 +1,18 @@
 <?xml version="1.0"?>
-<project
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	<modelVersion>4.0.0</modelVersion>
-	<parent>
-		<groupId>com.iluwatar</groupId>
-		<artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
-	</parent>
-	<artifactId>abstract-factory</artifactId>
-	<dependencies>
-		<dependency>
-			<groupId>junit</groupId>
-			<artifactId>junit</artifactId>
-			<scope>test</scope>
-		</dependency>
-	</dependencies>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.8.0</version>
+  </parent>
+  <artifactId>abstract-factory</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
 </project>

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

@@ -3,71 +3,108 @@ package com.iluwatar.abstractfactory;
 
 /**
  * 
- * The essence of the Abstract Factory pattern is a factory interface
- * ({@link KingdomFactory}) and its implementations ({@link ElfKingdomFactory},
- * {@link OrcKingdomFactory}).
+ * 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 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
-	 * @param factory
-	 */
-	public void createKingdom(final KingdomFactory factory) {
-		setKing(factory.createKing());
-		setCastle(factory.createCastle());
-		setArmy(factory.createArmy());
-	}
+
+  /**
+   * 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;
+  }
+  
+
+  /**
+   * 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());
 	
-	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;
-	}
+	  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());
+	  
+  }
+  
 }

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/index.md

@@ -4,9 +4,13 @@ title: Adapter
 folder: adapter
 permalink: /patterns/adapter/
 categories: Structural
-tags: Java
+tags:
+ - Java
+ - Gang Of Four
 ---
 
+**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.
@@ -22,3 +26,7 @@ incompatible interfaces.
 **Real world examples:**
 
 * [java.util.Arrays#asList()](http://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#asList%28T...%29)
+
+**Credits**
+
+* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)

adapter/pom.xml

@@ -1,19 +1,23 @@
 <?xml version="1.0"?>
-<project
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	<modelVersion>4.0.0</modelVersion>
-	<parent>
-		<groupId>com.iluwatar</groupId>
-		<artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
-	</parent>
-	<artifactId>adapter</artifactId>
-	<dependencies>
-		<dependency>
-			<groupId>junit</groupId>
-			<artifactId>junit</artifactId>
-			<scope>test</scope>
-		</dependency>
-	</dependencies>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.8.0</version>
+  </parent>
+  <artifactId>adapter</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <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

@@ -1,25 +1,28 @@
 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.
  * 
- * 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}).
+ * <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.
  * 
+ * <p>The Adapter ({@link GnomeEngineer}) converts the interface of the target class (
+ * {@link GoblinGlider}) into a suitable one expected by the client ({@link GnomeEngineeringManager}
+ * ).
  */
 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) {
+    Engineer manager = new GnomeEngineeringManager(new GnomeEngineer());
+    manager.operateDevice();
+  }
 }

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

@@ -7,6 +7,5 @@ package com.iluwatar.adapter;
  */
 public interface Engineer {
 
-	void operateDevice();
-
+  void operateDevice();
 }

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

@@ -2,23 +2,22 @@ package com.iluwatar.adapter;
 
 /**
  * 
- * Adapter class. Adapts the interface of the device ({@link GoblinGlider}) into
- * {@link Engineer} interface expected by the client ({@link GnomeEngineeringManager}).
+ * 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;
+  private GoblinGlider glider;
 
-	public GnomeEngineer() {
-		glider = new GoblinGlider();
-	}
-
-	@Override
-	public void operateDevice() {
-		glider.attachGlider();
-		glider.gainSpeed();
-		glider.takeOff();
-	}
+  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 +1,26 @@
 package com.iluwatar.adapter;
 
 /**
- * 
  * GnomeEngineering manager uses {@link Engineer} to operate devices.
- * 
  */
 public class GnomeEngineeringManager implements Engineer {
 
-	private Engineer engineer;
+  private Engineer engineer;
 
-	public GnomeEngineeringManager() {
-		engineer = new GnomeEngineer();
-	}
+  public GnomeEngineeringManager() {
 
-	@Override
-	public void operateDevice() {
-		engineer.operateDevice();
-	}
+  }
+
+  public GnomeEngineeringManager(Engineer engineer) {
+    this.engineer = engineer;
+  }
+
+  @Override
+  public void operateDevice() {
+    engineer.operateDevice();
+  }
+
+  public void setEngineer(Engineer engineer) {
+    this.engineer = engineer;
+  }
 }

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

@@ -7,15 +7,15 @@ package com.iluwatar.adapter;
  */
 public class GoblinGlider {
 
-	public void attachGlider() {
-		System.out.println("Glider attached.");
-	}
+  public void attachGlider() {
+    System.out.println("Glider attached.");
+  }
 
-	public void gainSpeed() {
-		System.out.println("Gaining speed.");
-	}
+  public void gainSpeed() {
+    System.out.println("Gaining speed.");
+  }
 
-	public void takeOff() {
-		System.out.println("Lift-off!");
-	}
+  public void takeOff() {
+    System.out.println("Lift-off!");
+  }
 }

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

@@ -0,0 +1,68 @@
+package com.iluwatar.adapter;
+
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * 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.
+ * 
+ * <p>The Adapter ({@link GnomeEngineer}) converts the interface 
+ * of the target class ({@link GoblinGlider}) into a suitable one expected by 
+ * the client ({@link GnomeEngineeringManager}
+ * ).
+ */
+public class AdapterPatternTest {
+
+  private Map<String, Object> beans;
+
+  private static final String ENGINEER_BEAN = "engineer";
+
+  private static final String MANAGER_BEAN = "manager";
+
+  /**
+   * This method runs before the test execution and sets the bean objects in the beans Map.
+   */
+  @Before
+  public void setup() {
+    beans = new HashMap<>();
+
+    GnomeEngineer gnomeEngineer = spy(new GnomeEngineer());
+    beans.put(ENGINEER_BEAN, gnomeEngineer);
+
+    GnomeEngineeringManager manager = new GnomeEngineeringManager();
+    manager.setEngineer((GnomeEngineer) beans.get(ENGINEER_BEAN));
+    beans.put(MANAGER_BEAN, manager);
+  }
+
+  /**
+   * This test asserts that when we call operateDevice() method on a manager bean, it is internally
+   * calling operateDevice method on the engineer object. The Adapter ({@link GnomeEngineer})
+   * converts the interface of the target class ( {@link GoblinGlider}) into a suitable one expected
+   * by the client ({@link GnomeEngineeringManager} ).
+   */
+  @Test
+  public void testAdapter() {
+    Engineer manager = (Engineer) beans.get(MANAGER_BEAN);
+
+    // when manager is asked to operate device
+    manager.operateDevice();
+
+    // Manager internally calls the engineer object to operateDevice
+    Engineer engineer = (Engineer) beans.get(ENGINEER_BEAN);
+    verify(engineer).operateDevice();
+  }
+}

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/pom.xml

@@ -1,19 +1,18 @@
 <?xml version="1.0"?>
-<project
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	<modelVersion>4.0.0</modelVersion>
-	<parent>
-		<groupId>com.iluwatar</groupId>
-		<artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
-	</parent>
-	<artifactId>async-method-invocation</artifactId>
-	<dependencies>
-		<dependency>
-			<groupId>junit</groupId>
-			<artifactId>junit</artifactId>
-			<scope>test</scope>
-		</dependency>
-	</dependencies>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.8.0</version>
+  </parent>
+  <artifactId>async-method-invocation</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
 </project>

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

@@ -4,23 +4,24 @@ 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>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.
  * <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 +33,68 @@ 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();
+  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

@@ -10,26 +10,26 @@ import java.util.concurrent.ExecutionException;
  */
 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);
+  }
 }

bridge/index.md

@@ -4,9 +4,13 @@ title: Bridge
 folder: bridge
 permalink: /patterns/bridge/
 categories: Structural
-tags: Java
+tags:
+ - Java
+ - Gang Of Four
 ---
 
+**Also known as:** Handle/Body
+
 **Intent:** Decouple an abstraction from its implementation so that the two can
 vary independently.
 
@@ -20,3 +24,7 @@ vary independently.
 * changes in the implementation of an abstraction should have no impact on clients; that is, their code should not have to be recompiled.
 * you have a proliferation of classes. Such a class hierarchy indicates the need for splitting an object into two parts. Rumbaugh uses the term "nested generalizations" to refer to such class hierarchies
 * you want to share an implementation among multiple objects (perhaps using reference counting), and this fact should be hidden from the client. A simple example is Coplien's String class, in which multiple objects can share the same string representation.
+
+**Credits**
+
+* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)

bridge/pom.xml

@@ -1,19 +1,18 @@
 <?xml version="1.0"?>
-<project
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	<modelVersion>4.0.0</modelVersion>
-	<parent>
-		<groupId>com.iluwatar</groupId>
-		<artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
-	</parent>
-	<artifactId>bridge</artifactId>
-	<dependencies>
-		<dependency>
-			<groupId>junit</groupId>
-			<artifactId>junit</artifactId>
-			<scope>test</scope>
-		</dependency>
-	</dependencies>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.8.0</version>
+  </parent>
+  <artifactId>bridge</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
 </project>

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

@@ -2,38 +2,38 @@ package com.iluwatar.bridge;
 
 /**
  * 
- * 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.
+ * 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.
  * 
  */
 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

@@ -11,9 +11,9 @@ 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);
+  }
 }

builder/index.md

@@ -4,7 +4,9 @@ title: Builder
 folder: builder
 permalink: /patterns/builder/
 categories: Creational
-tags: Java
+tags:
+ - Java
+ - Gang Of Four
 ---
 
 **Intent:** Separate the construction of a complex object from its
@@ -22,3 +24,7 @@ representations.
 
 * [java.lang.StringBuilder](http://docs.oracle.com/javase/8/docs/api/java/lang/StringBuilder.html)
 * [Apache Camel builders](https://github.com/apache/camel/tree/0e195428ee04531be27a0b659005e3aa8d159d23/camel-core/src/main/java/org/apache/camel/builder)
+
+**Credits**
+
+* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)

builder/pom.xml

@@ -1,19 +1,18 @@
 <?xml version="1.0"?>
-<project
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	<modelVersion>4.0.0</modelVersion>
-	<parent>
-		<groupId>com.iluwatar</groupId>
-		<artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
-	</parent>
-	<artifactId>builder</artifactId>
-	<dependencies>
-		<dependency>
-			<groupId>junit</groupId>
-			<artifactId>junit</artifactId>
-			<scope>test</scope>
-		</dependency>
-	</dependencies>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.8.0</version>
+  </parent>
+  <artifactId>builder</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
 </project>

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

@@ -1,42 +1,55 @@
 package com.iluwatar.builder;
 
-import com.iluwatar. builder.Hero.HeroBuilder;
+import com.iluwatar.builder.Hero.HeroBuilder;
 
 /**
  * 
- * This is the Builder pattern variation as described by Joshua Bloch in
- * Effective Java 2nd Edition.
+ * 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>
- * 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.
+ * 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.
+ * <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.
  * 
  */
 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 +7,122 @@ 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;
-		}
+    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

@@ -2,7 +2,7 @@ package com.iluwatar.builder;
 
 import org.junit.Test;
 
-import com.iluwatar. builder.App;
+import com.iluwatar.builder.App;
 
 /**
  * 
@@ -11,9 +11,9 @@ 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);
+  }
 }

business-delegate/pom.xml

@@ -6,7 +6,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+		<version>1.8.0</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/.gitignore

@@ -0,0 +1 @@
+/target/

caching/etc/caching.ucls

@@ -0,0 +1,106 @@
+<?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="main.java.com.wssia.caching.App" project="CachingPatterns" 
+    file="/CachingPatterns/src/main/java/com/wssia/caching/App.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="249" y="150"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="2" language="java" name="main.java.com.wssia.caching.AppManager" project="CachingPatterns" 
+    file="/CachingPatterns/src/main/java/com/wssia/caching/AppManager.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="502" y="163"/>    
+    <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="main.java.com.wssia.caching.CacheStore" project="CachingPatterns" 
+    file="/CachingPatterns/src/main/java/com/wssia/caching/CacheStore.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="537" y="436"/>    
+    <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>  
+  <enumeration id="4" language="java" name="main.java.com.wssia.caching.CachingPolicy" project="CachingPatterns" 
+    file="/CachingPatterns/src/main/java/com/wssia/caching/CachingPolicy.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="789" y="162"/>    
+    <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>  
+  </enumeration>  
+  <class id="5" language="java" name="main.java.com.wssia.caching.DBManager" project="CachingPatterns" 
+    file="/CachingPatterns/src/main/java/com/wssia/caching/DBManager.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="1137" y="134"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="6" language="java" name="main.java.com.wssia.caching.LRUCache" project="CachingPatterns" 
+    file="/CachingPatterns/src/main/java/com/wssia/caching/LRUCache.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="884" y="435"/>    
+    <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="7" language="java" name="main.java.com.wssia.caching.UserAccount" project="CachingPatterns" 
+    file="/CachingPatterns/src/main/java/com/wssia/caching/UserAccount.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="1140" y="405"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="8" language="java" name="test.java.com.wssia.caching.AppTest" project="CachingPatterns" 
+    file="/CachingPatterns/src/test/java/com/wssia/caching/AppTest.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="251" y="374"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <association id="9">    
+    <end type="SOURCE" refId="2" navigable="false">      
+      <attribute id="10" name="cachingPolicy"/>      
+      <multiplicity id="11" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="4" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <association id="12">    
+    <end type="SOURCE" refId="8" navigable="false">      
+      <attribute id="13" name="app"/>      
+      <multiplicity id="14" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="1" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <association id="15">    
+    <end type="SOURCE" refId="3" navigable="false">      
+      <attribute id="16" name="cache"/>      
+      <multiplicity id="17" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="6" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+    sort-features="false" accessors="true" visibility="true">    
+    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
+    <operations public="true" package="true" protected="true" private="true" static="true"/>  
+  </classifier-display>  
+  <association-display labels="true" multiplicity="true"/>
+</class-diagram>

caching/index.md

@@ -0,0 +1,24 @@
+---
+layout: pattern
+title: Caching
+folder: caching
+permalink: /patterns/caching/
+categories: Other
+tags:
+ - Java
+---
+
+**Intent:** To avoid expensive re-acquisition of resources by not releasing
+the resources immediately after their use. The resources retain their identity, are kept in some
+fast-access storage, and are re-used to avoid having to acquire them again.
+
+![alt text](./etc/caching.png "Caching")
+
+**Applicability:** Use the Caching pattern(s) when
+
+* Repetitious acquisition, initialization, and release of the same resource causes unnecessary performance overhead.
+
+**Credits**
+
+* [Write-through, write-around, write-back: Cache explained](http://www.computerweekly.com/feature/Write-through-write-around-write-back-Cache-explained)
+* [Read-Through, Write-Through, Write-Behind, and Refresh-Ahead Caching](https://docs.oracle.com/cd/E15357_01/coh.360/e15723/cache_rtwtwbra.htm#COHDG5177)

caching/pom.xml

@@ -0,0 +1,51 @@
+<?xml version="1.0"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.8.0</version>
+  </parent>
+  <artifactId>caching</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.mongodb</groupId>
+      <artifactId>mongodb-driver</artifactId>
+      <version>3.0.4</version>
+    </dependency>
+    <dependency>
+      <groupId>org.mongodb</groupId>
+      <artifactId>mongodb-driver-core</artifactId>
+      <version>3.0.4</version>
+    </dependency>
+    <dependency>
+      <groupId>org.mongodb</groupId>
+      <artifactId>bson</artifactId>
+      <version>3.0.4</version>
+    </dependency>
+  </dependencies>
+  <!--
+    Due to the use of MongoDB in the test of this pattern, TRAVIS and/or MAVEN might fail if the DB connection is
+    not open for the JUnit test. To avoid disrupting the compilation process, the surefire plug-in was used
+    to SKIP the running of the JUnit tests for this pattern. To ACTIVATE the running of the tests, change the
+    skipTests (below) flag to 'false' and vice-versa.
+  -->
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <version>2.19</version>
+        <configuration>
+          <skipTests>false</skipTests>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>

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

@@ -0,0 +1,117 @@
+package com.iluwatar.caching;
+
+/**
+ *
+ * The Caching pattern describes how to avoid expensive re-acquisition of resources by not releasing
+ * the resources immediately after their use. The resources retain their identity, are kept in some
+ * fast-access storage, and are re-used to avoid having to acquire them again. There are three main
+ * caching strategies/techniques in this pattern; each with their own pros and cons. They are:
+ * <code>write-through</code> which writes data to the cache and DB in a single transaction,
+ * <code>write-around</code> which writes data immediately into the DB instead of the cache, and
+ * <code>write-behind</code> which writes data into the cache initially whilst the data is only
+ * written into the DB when the cache is full. The <code>read-through</code> strategy is also
+ * included in the mentioned three strategies -- returns data from the cache to the caller <b>if</b>
+ * it exists <b>else</b> queries from DB and stores it into the cache for future use. These
+ * strategies determine when the data in the cache should be written back to the backing store (i.e.
+ * Database) and help keep both data sources synchronized/up-to-date. This pattern can improve
+ * performance and also helps to maintain consistency between data held in the cache and the data in
+ * the underlying data store.
+ * <p>
+ * In this example, the user account ({@link UserAccount}) entity is used as the underlying
+ * 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 (
+ * {@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
+ * (depending on the preferred caching policy/strategy).
+ *
+ * <i>App --> AppManager --> CacheStore/LRUCache/CachingPolicy --> DBManager</i>
+ * </p>
+ *
+ * @see CacheStore
+ * @See LRUCache
+ * @see CachingPolicy
+ *
+ */
+public class App {
+
+  /**
+   * Program entry point
+   *
+   * @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
+                              // 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).
+    AppManager.initCacheCapacity(3);
+    App app = new App();
+    app.useReadAndWriteThroughStrategy();
+    app.useReadThroughAndWriteAroundStrategy();
+    app.useReadThroughAndWriteBehindStrategy();
+  }
+
+  /**
+   * Read-through and write-through
+   */
+  public void useReadAndWriteThroughStrategy() {
+    System.out.println("# CachingPolicy.THROUGH");
+    AppManager.initCachingPolicy(CachingPolicy.THROUGH);
+
+    UserAccount userAccount1 = new UserAccount("001", "John", "He is a boy.");
+
+    AppManager.save(userAccount1);
+    System.out.println(AppManager.printCacheContent());
+    userAccount1 = AppManager.find("001");
+    userAccount1 = AppManager.find("001");
+  }
+
+  /**
+   * Read-through and write-around
+   */
+  public void useReadThroughAndWriteAroundStrategy() {
+    System.out.println("# CachingPolicy.AROUND");
+    AppManager.initCachingPolicy(CachingPolicy.AROUND);
+
+    UserAccount userAccount2 = new UserAccount("002", "Jane", "She is a girl.");
+
+    AppManager.save(userAccount2);
+    System.out.println(AppManager.printCacheContent());
+    userAccount2 = 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");
+    System.out.println(AppManager.printCacheContent());
+    userAccount2 = AppManager.find("002");
+  }
+
+  /**
+   * Read-through and write-behind
+   */
+  public void useReadThroughAndWriteBehindStrategy() {
+    System.out.println("# CachingPolicy.BEHIND");
+    AppManager.initCachingPolicy(CachingPolicy.BEHIND);
+
+    UserAccount userAccount3 = new UserAccount("003", "Adam", "He likes food.");
+    UserAccount userAccount4 = new UserAccount("004", "Rita", "She hates cats.");
+    UserAccount userAccount5 = new UserAccount("005", "Isaac", "He is allergic to mustard.");
+
+    AppManager.save(userAccount3);
+    AppManager.save(userAccount4);
+    AppManager.save(userAccount5);
+    System.out.println(AppManager.printCacheContent());
+    userAccount3 = 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");
+    System.out.println(AppManager.printCacheContent());
+  }
+}

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

@@ -0,0 +1,75 @@
+package com.iluwatar.caching;
+
+import java.text.ParseException;
+
+/**
+ *
+ * AppManager helps to bridge the gap in communication between the main class and the application's
+ * back-end. DB connection is initialized through this class. The chosen caching strategy/policy is
+ * also initialized here. Before the cache can be used, the size of the cache has to be set.
+ * Depending on the chosen caching policy, AppManager will call the appropriate function in the
+ * CacheStore class.
+ *
+ */
+public class AppManager {
+
+  private static CachingPolicy cachingPolicy;
+
+  /**
+   *
+   * 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) {
+      try {
+        DBManager.connect();
+      } catch (ParseException e) {
+        e.printStackTrace();
+      }
+    } else {
+      DBManager.createVirtualDB();
+    }
+  }
+
+  public static void initCachingPolicy(CachingPolicy policy) {
+    cachingPolicy = policy;
+    if (cachingPolicy == CachingPolicy.BEHIND) {
+      Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
+        @Override
+        public void run() {
+          CacheStore.flushCache();
+        }
+      }));
+    }
+    CacheStore.clearCache();
+  }
+
+  public static void initCacheCapacity(int capacity) {
+    CacheStore.initCapacity(capacity);
+  }
+
+  public static UserAccount find(String userID) {
+    if (cachingPolicy == CachingPolicy.THROUGH || cachingPolicy == CachingPolicy.AROUND) {
+      return CacheStore.readThrough(userID);
+    } else if (cachingPolicy == CachingPolicy.BEHIND) {
+      return CacheStore.readThroughWithWriteBackPolicy(userID);
+    }
+    return null;
+  }
+
+  public static void save(UserAccount userAccount) {
+    if (cachingPolicy == CachingPolicy.THROUGH) {
+      CacheStore.writeThrough(userAccount);
+    } else if (cachingPolicy == CachingPolicy.AROUND) {
+      CacheStore.writeAround(userAccount);
+    } else if (cachingPolicy == CachingPolicy.BEHIND) {
+      CacheStore.writeBehind(userAccount);
+    }
+  }
+
+  public static String printCacheContent() {
+    return CacheStore.print();
+  }
+}

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

@@ -0,0 +1,104 @@
+package com.iluwatar.caching;
+
+import java.util.ArrayList;
+
+/**
+ *
+ * The caching strategies are implemented in this class.
+ *
+ */
+public class CacheStore {
+
+  static LRUCache cache = null;
+
+  public static void initCapacity(int capacity) {
+    if (null == cache)
+      cache = new LRUCache(capacity);
+    else
+      cache.setCapacity(capacity);
+  }
+
+  public static UserAccount readThrough(String userID) {
+    if (cache.contains(userID)) {
+      System.out.println("# Cache Hit!");
+      return cache.get(userID);
+    }
+    System.out.println("# Cache Miss!");
+    UserAccount userAccount = DBManager.readFromDB(userID);
+    cache.set(userID, userAccount);
+    return userAccount;
+  }
+
+  public static void writeThrough(UserAccount userAccount) {
+    if (cache.contains(userAccount.getUserID())) {
+      DBManager.updateDB(userAccount);
+    } else {
+      DBManager.writeToDB(userAccount);
+    }
+    cache.set(userAccount.getUserID(), userAccount);
+  }
+
+  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
+                                                 // version from cache.
+    } else {
+      DBManager.writeToDB(userAccount);
+    }
+  }
+
+  public static UserAccount readThroughWithWriteBackPolicy(String userID) {
+    if (cache.contains(userID)) {
+      System.out.println("# Cache Hit!");
+      return cache.get(userID);
+    }
+    System.out.println("# Cache Miss!");
+    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);
+    }
+    cache.set(userID, userAccount);
+    return userAccount;
+  }
+
+  public static void writeBehind(UserAccount userAccount) {
+    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);
+    }
+    cache.set(userAccount.getUserID(), userAccount);
+  }
+
+  public static void clearCache() {
+    if (null != cache)
+      cache.clear();
+  }
+
+  /**
+   * Writes remaining content in the cache into the DB.
+   */
+  public static void flushCache() {
+    System.out.println("# flushCache...");
+    if (null == cache)
+      return;
+    ArrayList<UserAccount> listOfUserAccounts = cache.getCacheDataInListForm();
+    for (UserAccount userAccount : listOfUserAccounts) {
+      DBManager.upsertDB(userAccount);
+    }
+  }
+
+  public static String print() {
+    ArrayList<UserAccount> listOfUserAccounts = cache.getCacheDataInListForm();
+    StringBuilder sb = new StringBuilder();
+    sb.append("\n--CACHE CONTENT--\n");
+    for (UserAccount userAccount : listOfUserAccounts) {
+      sb.append(userAccount.toString() + "\n");
+    }
+    sb.append("----\n");
+    return sb.toString();
+  }
+}

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

@@ -0,0 +1,20 @@
+package com.iluwatar.caching;
+
+/**
+ *
+ * Enum class containing the three caching strategies implemented in the pattern.
+ *
+ */
+public enum CachingPolicy {
+  THROUGH("through"), AROUND("around"), BEHIND("behind");
+
+  private String policy;
+
+  private CachingPolicy(String policy) {
+    this.policy = policy;
+  }
+
+  public String getPolicy() {
+    return policy;
+  }
+}

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

@@ -0,0 +1,123 @@
+package com.iluwatar.caching;
+
+import java.text.ParseException;
+import java.util.HashMap;
+
+import org.bson.Document;
+
+import com.mongodb.MongoClient;
+import com.mongodb.client.FindIterable;
+import com.mongodb.client.MongoDatabase;
+import com.mongodb.client.model.UpdateOptions;
+
+/**
+ *
+ * <p>DBManager handles the communication with the underlying data store i.e. Database. It contains the
+ * implemented methods for querying, inserting, and updating data. MongoDB was used as the database
+ * for the application.</p>
+ * 
+ * <p>Developer/Tester is able to choose whether the application should use MongoDB as its underlying
+ * data storage (connect()) or a simple Java data structure to (temporarily) store the data/objects
+ * during runtime (createVirtualDB()).</p>
+ * 
+ */
+public class DBManager {
+
+  private static MongoClient mongoClient;
+  private static MongoDatabase db;
+  private static boolean useMongoDB;
+
+  private static HashMap<String, UserAccount> virtualDB;
+
+  public static void createVirtualDB() {
+    useMongoDB = false;
+    virtualDB = new HashMap<String, UserAccount>();
+  }
+
+  public static void connect() throws ParseException {
+    useMongoDB = true;
+    mongoClient = new MongoClient();
+    db = mongoClient.getDatabase("test");
+  }
+
+  public static UserAccount readFromDB(String userID) {
+    if (!useMongoDB) {
+      if (virtualDB.containsKey(userID))
+        return virtualDB.get(userID);
+      return null;
+    }
+    if (null == db) {
+      try {
+        connect();
+      } catch (ParseException e) {
+        e.printStackTrace();
+      }
+    }
+    FindIterable<Document> iterable =
+        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"));
+    return userAccount;
+  }
+
+  public static void writeToDB(UserAccount userAccount) {
+    if (!useMongoDB) {
+      virtualDB.put(userAccount.getUserID(), userAccount);
+      return;
+    }
+    if (null == db) {
+      try {
+        connect();
+      } catch (ParseException e) {
+        e.printStackTrace();
+      }
+    }
+    db.getCollection("user_accounts").insertOne(
+        new Document("userID", userAccount.getUserID()).append("userName",
+            userAccount.getUserName()).append("additionalInfo", userAccount.getAdditionalInfo()));
+  }
+
+  public static void updateDB(UserAccount userAccount) {
+    if (!useMongoDB) {
+      virtualDB.put(userAccount.getUserID(), userAccount);
+      return;
+    }
+    if (null == db) {
+      try {
+        connect();
+      } catch (ParseException e) {
+        e.printStackTrace();
+      }
+    }
+    db.getCollection("user_accounts").updateOne(
+        new Document("userID", userAccount.getUserID()),
+        new Document("$set", new Document("userName", userAccount.getUserName()).append(
+            "additionalInfo", userAccount.getAdditionalInfo())));
+  }
+
+  /**
+   *
+   * Insert data into DB if it does not exist. Else, update it.
+   */
+  public static void upsertDB(UserAccount userAccount) {
+    if (!useMongoDB) {
+      virtualDB.put(userAccount.getUserID(), userAccount);
+      return;
+    }
+    if (null == db) {
+      try {
+        connect();
+      } catch (ParseException e) {
+        e.printStackTrace();
+      }
+    }
+    db.getCollection("user_accounts").updateOne(
+        new Document("userID", userAccount.getUserID()),
+        new Document("$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

@@ -0,0 +1,146 @@
+package com.iluwatar.caching;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+
+/**
+ *
+ * Data structure/implementation of the application's cache. The data structure consists of a hash
+ * table attached with a doubly linked-list. The linked-list helps in capturing and maintaining the
+ * LRU data in the cache. When a data is queried (from the cache), added (to the cache), or updated,
+ * the data is moved to the front of the list to depict itself as the most-recently-used data. The
+ * LRU data is always at the end of the list.
+ *
+ */
+public class LRUCache {
+
+  class Node {
+    String userID;
+    UserAccount userAccount;
+    Node previous;
+    Node next;
+
+    public Node(String userID, UserAccount userAccount) {
+      this.userID = userID;
+      this.userAccount = userAccount;
+    }
+  }
+
+  int capacity;
+  HashMap<String, Node> cache = new HashMap<String, Node>();
+  Node head = null;
+  Node end = null;
+
+  public LRUCache(int capacity) {
+    this.capacity = capacity;
+  }
+
+  public UserAccount get(String userID) {
+    if (cache.containsKey(userID)) {
+      Node node = cache.get(userID);
+      remove(node);
+      setHead(node);
+      return node.userAccount;
+    }
+    return null;
+  }
+
+  /**
+   *
+   * Remove node from linked list.
+   */
+  public void remove(Node node) {
+    if (node.previous != null) {
+      node.previous.next = node.next;
+    } else {
+      head = node.next;
+    }
+    if (node.next != null) {
+      node.next.previous = node.previous;
+    } else {
+      end = node.previous;
+    }
+  }
+
+  /**
+   *
+   * Move node to the front of the list.
+   */
+  public void setHead(Node node) {
+    node.next = head;
+    node.previous = null;
+    if (head != null)
+      head.previous = node;
+    head = node;
+    if (end == null)
+      end = head;
+  }
+
+  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);
+      if (cache.size() >= capacity) {
+        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);
+    }
+  }
+
+  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);
+    remove(toBeRemoved);
+    cache.remove(userID);
+  }
+
+  public boolean isFull() {
+    return cache.size() >= capacity;
+  }
+
+  public UserAccount getLRUData() {
+    return end.userAccount;
+  }
+
+  public void clear() {
+    head = null;
+    end = null;
+    cache.clear();
+  }
+
+  /**
+   *
+   * Returns cache data in list form.
+   */
+  public ArrayList<UserAccount> getCacheDataInListForm() {
+    ArrayList<UserAccount> listOfCacheData = new ArrayList<UserAccount>();
+    Node temp = head;
+    while (temp != null) {
+      listOfCacheData.add(temp.userAccount);
+      temp = temp.next;
+    }
+    return listOfCacheData;
+  }
+
+  public void setCapacity(int newCapacity) {
+    if (capacity > newCapacity) {
+      clear(); // Behavior can be modified to accommodate for decrease in cache size. For now, we'll
+               // just clear the cache.
+    } else {
+      this.capacity = newCapacity;
+    }
+  }
+}

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

@@ -0,0 +1,47 @@
+package com.iluwatar.caching;
+
+/**
+ *
+ * Entity class (stored in cache and DB) used in the application.
+ *
+ */
+public class UserAccount {
+  private String userID;
+  private String userName;
+  private String additionalInfo;
+
+  public UserAccount(String userID, String userName, String additionalInfo) {
+    this.userID = userID;
+    this.userName = userName;
+    this.additionalInfo = additionalInfo;
+  }
+
+  public String getUserID() {
+    return userID;
+  }
+
+  public void setUserID(String userID) {
+    this.userID = userID;
+  }
+
+  public String getUserName() {
+    return userName;
+  }
+
+  public void setUserName(String userName) {
+    this.userName = userName;
+  }
+
+  public String getAdditionalInfo() {
+    return additionalInfo;
+  }
+
+  public void setAdditionalInfo(String additionalInfo) {
+    this.additionalInfo = additionalInfo;
+  }
+
+  @Override
+  public String toString() {
+    return userID + ", " + userName + ", " + additionalInfo;
+  }
+}

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

@@ -0,0 +1,41 @@
+package com.iluwatar.caching;
+
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ *
+ * Application test
+ *
+ */
+public class AppTest {
+  App app;
+
+  /**
+   * Setup of application test includes: initializing DB connection and cache size/capacity.
+   */
+  @Before
+  public void setUp() {
+    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).
+    AppManager.initCacheCapacity(3);
+    app = new App();
+  }
+
+  @Test
+  public void testReadAndWriteThroughStrategy() {
+    app.useReadAndWriteThroughStrategy();
+  }
+
+  @Test
+  public void testReadThroughAndWriteAroundStrategy() {
+    app.useReadThroughAndWriteAroundStrategy();
+  }
+
+  @Test
+  public void testReadThroughAndWriteBehindStrategy() {
+    app.useReadThroughAndWriteBehindStrategy();
+  }
+}

callback/pom.xml

@@ -1,19 +1,18 @@
 <?xml version="1.0"?>
-<project
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	<modelVersion>4.0.0</modelVersion>
-	<parent>
-		<groupId>com.iluwatar</groupId>
-		<artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
-	</parent>
-	<artifactId>callback</artifactId>
-	<dependencies>
-		<dependency>
-			<groupId>junit</groupId>
-			<artifactId>junit</artifactId>
-			<scope>test</scope>
-		</dependency>
-	</dependencies>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.8.0</version>
+  </parent>
+  <artifactId>callback</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
 </project>

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

@@ -2,20 +2,21 @@ 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);
-	}
+  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();
+  public 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.");
-	}
-
+  @Override
+  public void execute() {
+    System.out.println("Perform some important activity and after call the callback method.");
+  }
 }

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

@@ -7,12 +7,12 @@ package com.iluwatar.callback;
  */
 public abstract class Task {
 
-	public final void executeWith(Callback callback) {
-		execute();
-		if (callback != null) {
-			callback.call();
-		}
-	}
+  public final void executeWith(Callback callback) {
+    execute();
+    if (callback != null) {
+      callback.call();
+    }
+  }
 
-	public abstract void execute();
+  public abstract void execute();
 }

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

@@ -2,18 +2,38 @@ package com.iluwatar.callback;
 
 import org.junit.Test;
 
-import com.iluwatar.callback.App;
+import static org.junit.Assert.assertEquals;
 
 /**
- * 
- * Application test
+ * Add a field as a counter. Every time the callback method is called increment this field. Unit
+ * test checks that the field is being incremented.
  *
+ * Could be done with mock objects as well where the call method call is verified.
  */
 public class AppTest {
 
-	@Test
-	public void test() {
-		String[] args = {};
-		App.main(args);
-	}
+  private Integer callingCount = 0;
+
+  @Test
+  public void test() {
+    Callback callback = new Callback() {
+      @Override
+      public void call() {
+        callingCount++;
+      }
+    };
+
+    Task task = new SimpleTask();
+
+    assertEquals("Initial calling count of 0", new Integer(0), callingCount);
+
+    task.executeWith(callback);
+
+    assertEquals("Callback called once", new Integer(1), callingCount);
+
+    task.executeWith(callback);
+
+    assertEquals("Callback called twice", new Integer(2), callingCount);
+
+  }
 }

chain/index.md

@@ -4,7 +4,9 @@ title: Chain of responsibility
 folder: chain
 permalink: /patterns/chain/
 categories: Behavioral
-tags: Java
+tags:
+ - Java
+ - Gang Of Four
 ---
 
 **Intent:** Avoid coupling the sender of a request to its receiver by giving
@@ -23,3 +25,7 @@ objects and pass the request along the chain until an object handles it.
 
 * [java.util.logging.Logger#log()](http://docs.oracle.com/javase/8/docs/api/java/util/logging/Logger.html#log%28java.util.logging.Level,%20java.lang.String%29)
 * [Apache Commons Chain](https://commons.apache.org/proper/commons-chain/index.html)
+
+**Credits**
+
+* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)

chain/pom.xml

@@ -1,19 +1,18 @@
 <?xml version="1.0"?>
-<project
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	<modelVersion>4.0.0</modelVersion>
-	<parent>
-		<groupId>com.iluwatar</groupId>
-		<artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
-	</parent>
-	<artifactId>chain</artifactId>
-	<dependencies>
-		<dependency>
-			<groupId>junit</groupId>
-			<artifactId>junit</artifactId>
-			<scope>test</scope>
-		</dependency>
-	</dependencies>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.8.0</version>
+  </parent>
+  <artifactId>chain</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
 </project>

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

@@ -2,25 +2,30 @@ package com.iluwatar.chain;
 
 /**
  * 
- * Chain of Responsibility organizes request handlers ({@link RequestHandler}) into a
- * chain where each handler has a chance to act on the request on its turn. In
- * this example the king ({@link OrcKing}) makes requests and the military orcs
- * ({@link OrcCommander}, {@link OrcOfficer}, {@link OrcSoldier}) form the handler chain.
+ * The Chain of Responsibility pattern is a design pattern consisting of command objects and a
+ * series of processing objects. Each processing object contains logic that defines the types of
+ * command objects that it can handle; the rest are passed to the next processing object in the
+ * chain. A mechanism also exists for adding new processing objects to the end of this chain.
+ * <p>
+ * In this example we organize the request handlers ({@link RequestHandler}) into a chain where each
+ * handler has a chance to act on the request on its turn. Here the king ({@link OrcKing}) makes
+ * requests and the military orcs ({@link OrcCommander}, {@link OrcOfficer}, {@link OrcSoldier})
+ * form the handler chain.
  * 
  */
 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) {
 
-		OrcKing king = new OrcKing();
-		king.makeRequest(new Request(RequestType.DEFEND_CASTLE, "defend castle"));
-		king.makeRequest(new Request(RequestType.TORTURE_PRISONER,
-				"torture prisoner"));
-		king.makeRequest(new Request(RequestType.COLLECT_TAX, "collect tax"));
+    OrcKing king = new OrcKing();
+    king.makeRequest(new Request(RequestType.DEFEND_CASTLE, "defend castle"));
+    king.makeRequest(new Request(RequestType.TORTURE_PRISONER, "torture prisoner"));
+    king.makeRequest(new Request(RequestType.COLLECT_TAX, "collect tax"));
 
-	}
+  }
 }

chain/src/main/java/com/iluwatar/chain/OrcCommander.java

@@ -7,21 +7,21 @@ package com.iluwatar.chain;
  */
 public class OrcCommander extends RequestHandler {
 
-	public OrcCommander(RequestHandler handler) {
-		super(handler);
-	}
+  public OrcCommander(RequestHandler handler) {
+    super(handler);
+  }
 
-	@Override
-	public void handleRequest(Request req) {
-		if (req.getRequestType().equals(RequestType.DEFEND_CASTLE)) {
-			printHandling(req);
-		} else {
-			super.handleRequest(req);
-		}
-	}
+  @Override
+  public void handleRequest(Request req) {
+    if (req.getRequestType().equals(RequestType.DEFEND_CASTLE)) {
+      printHandling(req);
+    } else {
+      super.handleRequest(req);
+    }
+  }
 
-	@Override
-	public String toString() {
-		return "Orc commander";
-	}
+  @Override
+  public String toString() {
+    return "Orc commander";
+  }
 }

chain/src/main/java/com/iluwatar/chain/OrcKing.java

@@ -7,18 +7,18 @@ package com.iluwatar.chain;
  */
 public class OrcKing {
 
-	RequestHandler chain;
+  RequestHandler chain;
 
-	public OrcKing() {
-		buildChain();
-	}
+  public OrcKing() {
+    buildChain();
+  }
 
-	private void buildChain() {
-		chain = new OrcCommander(new OrcOfficer(new OrcSoldier(null)));
-	}
+  private void buildChain() {
+    chain = new OrcCommander(new OrcOfficer(new OrcSoldier(null)));
+  }
 
-	public void makeRequest(Request req) {
-		chain.handleRequest(req);
-	}
+  public void makeRequest(Request req) {
+    chain.handleRequest(req);
+  }
 
 }

chain/src/main/java/com/iluwatar/chain/OrcOfficer.java

@@ -7,22 +7,22 @@ package com.iluwatar.chain;
  */
 public class OrcOfficer extends RequestHandler {
 
-	public OrcOfficer(RequestHandler handler) {
-		super(handler);
-	}
+  public OrcOfficer(RequestHandler handler) {
+    super(handler);
+  }
 
-	@Override
-	public void handleRequest(Request req) {
-		if (req.getRequestType().equals(RequestType.TORTURE_PRISONER)) {
-			printHandling(req);
-		} else {
-			super.handleRequest(req);
-		}
-	}
+  @Override
+  public void handleRequest(Request req) {
+    if (req.getRequestType().equals(RequestType.TORTURE_PRISONER)) {
+      printHandling(req);
+    } else {
+      super.handleRequest(req);
+    }
+  }
 
-	@Override
-	public String toString() {
-		return "Orc officer";
-	}
+  @Override
+  public String toString() {
+    return "Orc officer";
+  }
 
 }

chain/src/main/java/com/iluwatar/chain/OrcSoldier.java

@@ -7,21 +7,21 @@ package com.iluwatar.chain;
  */
 public class OrcSoldier extends RequestHandler {
 
-	public OrcSoldier(RequestHandler handler) {
-		super(handler);
-	}
+  public OrcSoldier(RequestHandler handler) {
+    super(handler);
+  }
 
-	@Override
-	public void handleRequest(Request req) {
-		if (req.getRequestType().equals(RequestType.COLLECT_TAX)) {
-			printHandling(req);
-		} else {
-			super.handleRequest(req);
-		}
-	}
+  @Override
+  public void handleRequest(Request req) {
+    if (req.getRequestType().equals(RequestType.COLLECT_TAX)) {
+      printHandling(req);
+    } else {
+      super.handleRequest(req);
+    }
+  }
 
-	@Override
-	public String toString() {
-		return "Orc soldier";
-	}
+  @Override
+  public String toString() {
+    return "Orc soldier";
+  }
 }

chain/src/main/java/com/iluwatar/chain/Request.java

@@ -7,32 +7,32 @@ package com.iluwatar.chain;
  */
 public class Request {
 
-	private String requestDescription;
-	private RequestType requestType;
+  private String requestDescription;
+  private RequestType requestType;
 
-	public Request(RequestType requestType, String requestDescription) {
-		this.setRequestType(requestType);
-		this.setRequestDescription(requestDescription);
-	}
+  public Request(RequestType requestType, String requestDescription) {
+    this.setRequestType(requestType);
+    this.setRequestDescription(requestDescription);
+  }
 
-	public String getRequestDescription() {
-		return requestDescription;
-	}
+  public String getRequestDescription() {
+    return requestDescription;
+  }
 
-	public void setRequestDescription(String requestDescription) {
-		this.requestDescription = requestDescription;
-	}
+  public void setRequestDescription(String requestDescription) {
+    this.requestDescription = requestDescription;
+  }
 
-	public RequestType getRequestType() {
-		return requestType;
-	}
+  public RequestType getRequestType() {
+    return requestType;
+  }
 
-	public void setRequestType(RequestType requestType) {
-		this.requestType = requestType;
-	}
+  public void setRequestType(RequestType requestType) {
+    this.requestType = requestType;
+  }
 
-	@Override
-	public String toString() {
-		return getRequestDescription();
-	}
+  @Override
+  public String toString() {
+    return getRequestDescription();
+  }
 }

chain/src/main/java/com/iluwatar/chain/RequestHandler.java

@@ -7,22 +7,22 @@ package com.iluwatar.chain;
  */
 public abstract class RequestHandler {
 
-	private RequestHandler next;
+  private RequestHandler next;
 
-	public RequestHandler(RequestHandler next) {
-		this.next = next;
-	}
+  public RequestHandler(RequestHandler next) {
+    this.next = next;
+  }
 
-	public void handleRequest(Request req) {
-		if (next != null) {
-			next.handleRequest(req);
-		}
-	}
+  public void handleRequest(Request req) {
+    if (next != null) {
+      next.handleRequest(req);
+    }
+  }
 
-	protected void printHandling(Request req) {
-		System.out.println(this + " handling request \"" + req + "\"");
-	}
+  protected void printHandling(Request req) {
+    System.out.println(this + " handling request \"" + req + "\"");
+  }
 
-	@Override
-	public abstract String toString();
+  @Override
+  public abstract String toString();
 }

chain/src/main/java/com/iluwatar/chain/RequestType.java

@@ -7,6 +7,6 @@ package com.iluwatar.chain;
  */
 public enum RequestType {
 
-	DEFEND_CASTLE, TORTURE_PRISONER, COLLECT_TAX
+  DEFEND_CASTLE, TORTURE_PRISONER, COLLECT_TAX
 
 }