Achieved milestone 1.9.0

Add unit tests for remaining patterns

.travis.yml

@@ -1,20 +1,18 @@
 language: java
-
 jdk:
 - oraclejdk8
 
 env:
   global:
   - GH_REF: github.com/iluwatar/java-design-patterns.git
-  - secure: "LxTDuNS/rBWIvKkaEqr79ImZAe48mCdoYCF41coxNXgNoippo4GIBArknqtv+XvdkiuRZ1yGyj6pn8GU33c/yn+krddTUkVCwTbVatbalW5jhQjDbHYym/JcxaK9ZS/3JTeGcWrBgiPqHEEDhCf26vPZsXoMSeVCEORVKTp1BSg="
+  - secure: LxTDuNS/rBWIvKkaEqr79ImZAe48mCdoYCF41coxNXgNoippo4GIBArknqtv+XvdkiuRZ1yGyj6pn8GU33c/yn+krddTUkVCwTbVatbalW5jhQjDbHYym/JcxaK9ZS/3JTeGcWrBgiPqHEEDhCf26vPZsXoMSeVCEORVKTp1BSg=
   
 before_install:
-  - "export DISPLAY=:99.0"
+- export DISPLAY=:99.0
-  - "sh -e /etc/init.d/xvfb start"
+- 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 
+
+

CONTRIBUTING.MD

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

README.md

@@ -2,11 +2,10 @@
      that smart and dearly wants an empty line before a heading to be able to
      display it as such, e.g. website) -->
 
-# Design pattern samples in Java
+# Design patterns implemented in Java
 
 [![Build status](https://travis-ci.org/iluwatar/java-design-patterns.svg?branch=master)](https://travis-ci.org/iluwatar/java-design-patterns)
 [![Coverage Status](https://coveralls.io/repos/iluwatar/java-design-patterns/badge.svg?branch=master)](https://coveralls.io/r/iluwatar/java-design-patterns?branch=master)
-[![Coverity Scan Build Status](https://scan.coverity.com/projects/5634/badge.svg)](https://scan.coverity.com/projects/5634)
 [![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 # Introduction
@@ -26,7 +25,13 @@ are familiar with the patterns.
 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.
@@ -34,11 +39,10 @@ Once you are familiar with these concepts you can start drilling down into patte
 
 # How to contribute
 
-If you are willing to contribute to the project you will find the relevant information in our [developer wiki](https://github.com/iluwatar/java-design-patterns/wiki).
+If you are willing to contribute to the project you will find the relevant information in our [developer wiki](https://github.com/iluwatar/java-design-patterns/wiki). We will help you and answer your questions in the [Gitter chatroom](https://gitter.im/iluwatar/java-design-patterns).
 
 # Credits
 
-* [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 +52,6 @@ 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 +4,14 @@ title: Abstract Factory
 folder: abstract-factory
 permalink: /patterns/abstract-factory/
 categories: Creational
-tags: Java
+tags: 
+ - Java
+ - Gang Of Four
+ - Difficulty-Intermediate
 ---
 
+**Also known as:** Kit
+
 **Intent:** Provide an interface for creating families of related or dependent
 objects without specifying their concrete classes.
 
@@ -22,3 +27,7 @@ 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

@@ -1,12 +1,11 @@
 <?xml version="1.0"?>
-<project
+<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"
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <modelVersion>4.0.0</modelVersion>
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>abstract-factory</artifactId>
   <dependencies>

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

@@ -1,14 +1,18 @@
 package com.iluwatar.abstractfactory;
 
-
 /**
  * 
- * The essence of the Abstract Factory pattern is a factory interface
+ * The Abstract Factory pattern provides a way to encapsulate a group of individual factories that have a common theme
- * ({@link KingdomFactory}) and its implementations ({@link ElfKingdomFactory},
+ * without specifying their concrete classes. In normal usage, the client software creates a concrete implementation of
- * {@link OrcKingdomFactory}).
+ * 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
+ * The essence of the Abstract Factory pattern is a factory interface ({@link KingdomFactory}) and its implementations (
- * an army.
+ * {@link ElfKingdomFactory}, {@link OrcKingdomFactory}). The example uses both concrete implementations to create a
+ * king, a castle and an army.
  * 
  */
 public class App {
@@ -19,7 +23,6 @@ public class App {
 
   /**
    * Creates kingdom
-	 * @param factory
    */
   public void createKingdom(final KingdomFactory factory) {
     setKing(factory.createKing());
@@ -39,14 +42,6 @@ public class App {
     return factory.createKing();
   }
 
-	Castle getCastle(final KingdomFactory factory) {
-		return factory.createCastle();
-	}
-	
-	Army getArmy(final KingdomFactory factory) {
-		return factory.createArmy();
-	}
-	
   public King getKing() {
     return king;
   }
@@ -55,6 +50,10 @@ public class App {
     this.king = king;
   }
   
+  Castle getCastle(final KingdomFactory factory) {
+    return factory.createCastle();
+  }
+
   public Castle getCastle() {
     return castle;
   }
@@ -63,6 +62,10 @@ public class App {
     this.castle = castle;
   }
   
+  Army getArmy(final KingdomFactory factory) {
+    return factory.createArmy();
+  }
+
   public Army getArmy() {
     return army;
   }
@@ -70,4 +73,33 @@ public class App {
   private void setArmy(final Army army) {
     this.army = army;
   }
+  
+  /**
+   * Program entry point
+   * 
+   * @param args
+   *          command line args
+   */
+  public static void main(String[] args) {
+
+    App app = new App();
+
+    System.out.println("Elf Kingdom");
+    KingdomFactory elfKingdomFactory;
+    elfKingdomFactory = app.getElfKingdomFactory();
+    app.createKingdom(elfKingdomFactory);
+    System.out.println(app.getArmy().getDescription());
+    System.out.println(app.getCastle().getDescription());
+    System.out.println(app.getKing().getDescription());
+
+    System.out.println("\nOrc Kingdom");
+    KingdomFactory orcKingdomFactory;
+    orcKingdomFactory = app.getOrcKingdomFactory();
+    app.createKingdom(orcKingdomFactory);
+    System.out.println(app.getArmy().getDescription());
+    System.out.println(app.getCastle().getDescription());
+    System.out.println(app.getKing().getDescription());
+
+  }
+
 }

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

@@ -18,5 +18,4 @@ public class OrcKingdomFactory implements KingdomFactory {
   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;
 
@@ -7,7 +8,7 @@ import org.junit.Test;
 
 public class AppTest {
 
-	private App app = new App();;
+  private App app = new App();
   private KingdomFactory elfFactory;
   private KingdomFactory orcFactory;
 

adapter/etc/adapter.ucls

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

adapter/index.md

@@ -4,14 +4,19 @@ title: Adapter
 folder: adapter
 permalink: /patterns/adapter/
 categories: Structural
-tags: Java
+tags:
+ - Java
+ - Gang Of Four
+ - Difficulty-Beginner
 ---
 
+**Also known as:** Wrapper
+
 **Intent:** Convert the interface of a class into another interface the clients
 expect. Adapter lets classes work together that couldn't otherwise because of
 incompatible interfaces.
 
-![alt text](./etc/adapter_1.png "Adapter")
+![alt text](./etc/adapter.png "Adapter")
 
 **Applicability:** Use the Adapter pattern when
 
@@ -22,3 +27,7 @@ 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

@@ -1,12 +1,11 @@
 <?xml version="1.0"?>
-<project
+<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"
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <modelVersion>4.0.0</modelVersion>
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>adapter</artifactId>
   <dependencies>
@@ -15,5 +14,10 @@
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

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

@@ -1,25 +1,38 @@
 package com.iluwatar.adapter;
 
 /**
+ * An adapter helps two incompatible interfaces to work together. This is the real world definition
+ * for an adapter. Interfaces may be incompatible but the inner functionality should suit the need.
+ * The Adapter design pattern allows otherwise incompatible classes to work together by converting
+ * the interface of one class into an interface expected by the clients.
  *
- * 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
+ * There are two variations of the Adapter pattern: The class adapter implements the adaptee's
- * ({@link GoblinGlider}) into a suitable one expected by the client
+ * interface whereas the object adapter uses composition to contain the adaptee in the adapter
- * ({@link GnomeEngineeringManager}).
+ * object. This example uses the object adapter approach.
+ *
+ * <p>
+ * The Adapter ({@link BattleFishingBoat}) converts the interface of the adaptee class (
+ * {@link FishingBoat}) into a suitable one expected by the client ( {@link BattleShip} ).
+ *
+ * <p>
+ * The story of this implementation is this. <br>
+ * Pirates are coming! we need a {@link BattleShip} to fight! We have a {@link FishingBoat} and our
+ * captain. We have no time to make up a new ship! we need to reuse this {@link FishingBoat}. The
+ * captain needs a battleship which can fire and move. The spec is in {@link BattleShip}. We will
+ * use the Adapter pattern to reuse {@link FishingBoat}.
  *
  */
 public class App {
 
   /**
-	 * Program entry point
+   * Program entry point.
+   *
    * @param args command line args
    */
   public static void main(String[] args) {
-		Engineer manager = new GnomeEngineeringManager();
+    Captain captain = new Captain(new BattleFishingBoat());
-		manager.operateDevice();
+    captain.move();
+    captain.fire();
   }
 }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

async-method-invocation/index.md

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

async-method-invocation/pom.xml

@@ -1,12 +1,11 @@
 <?xml version="1.0"?>
-<project
+<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"
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <modelVersion>4.0.0</modelVersion>
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>async-method-invocation</artifactId>
   <dependencies>
@@ -15,5 +14,10 @@
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

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

@@ -5,22 +5,22 @@ import java.util.concurrent.Callable;
 /**
  * This application demonstrates the async method invocation pattern. Key parts of the pattern are
  * <code>AsyncResult</code> which is an intermediate container for an asynchronously evaluated value,
- * <code>AsyncCallback</code> which can be provided to be executed on task completion and
+ * <code>AsyncCallback</code> which can be provided to be executed on task completion and <code>AsyncExecutor</code>
- * <code>AsyncExecutor</code> that manages the execution of the async tasks.
+ * 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
+ * The main method shows example flow of async invocations. The main thread starts multiple tasks with variable
- * variable durations and then continues its own work. When the main thread has done it's job it collects
+ * durations and then continues its own work. When the main thread has done it's job it collects the results of the
- * the results of the async tasks. Two of the tasks are handled with callbacks, meaning the callbacks are
+ * async tasks. Two of the tasks are handled with callbacks, meaning the callbacks are executed immediately when the
- * executed immediately when the tasks complete.
+ * tasks complete.
  * <p>
- * Noteworthy difference of thread usage between the async results and callbacks is that the async results
+ * Noteworthy difference of thread usage between the async results and callbacks is that the async results are collected
- * are collected in the main thread but the callbacks are executed within the worker threads. This should be
+ * in the main thread but the callbacks are executed within the worker threads. This should be noted when working with
- * noted when working with thread pools.
+ * thread pools.
  * <p>
- * Java provides its own implementations of async method invocation pattern. FutureTask, CompletableFuture
+ * Java provides its own implementations of async method invocation pattern. FutureTask, CompletableFuture and
- * and ExecutorService are the real world implementations of this pattern. But due to the nature of parallel
+ * ExecutorService are the real world implementations of this pattern. But due to the nature of parallel programming,
- * programming, the implementations are not trivial. This example does not take all possible scenarios into
+ * the implementations are not trivial. This example does not take all possible scenarios into account but rather
- * account but rather provides a simple version that helps to understand the pattern.
+ * provides a simple version that helps to understand the pattern.
  *
  * @see AsyncResult
  * @see AsyncCallback
@@ -32,6 +32,9 @@ import java.util.concurrent.Callable;
  */
 public class App {
 
+  /**
+   * Program entry point
+   */
   public static void main(String[] args) throws Exception {
     // construct a new executor that will run async tasks
     AsyncExecutor executor = new ThreadAsyncExecutor();
@@ -63,8 +66,10 @@ public class App {
   /**
    * Creates a callable that lazily evaluates to given value with artificial delay.
    *
-	 * @param value value to evaluate
+   * @param value
-	 * @param delayMillis artificial delay in milliseconds
+   *          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) {
@@ -78,7 +83,8 @@ public class App {
   /**
    * Creates a simple callback that logs the complete status of the async result.
    *
-	 * @param name callback name
+   * @param name
+   *          callback name
    * @return new async callback
    */
   private static <T> AsyncCallback<T> callback(String name) {

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

@@ -18,5 +18,4 @@ public interface AsyncCallback<T> {
    * @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

@@ -38,5 +38,4 @@ public interface AsyncExecutor {
    * @throws InterruptedException if the execution is interrupted
    */
   <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException;
-
 }

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

@@ -5,8 +5,6 @@ import java.util.concurrent.ExecutionException;
 /**
  * 
  * AsyncResult interface
- *
- * @param <T>
  */
 public interface AsyncResult<T> {
 

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

@@ -44,9 +44,8 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
   }
 
   /**
-	 * Simple implementation of async result that allows completing it successfully with a value
+   * Simple implementation of async result that allows completing it successfully with a value or exceptionally with an
-	 * or exceptionally with an exception. A really simplified version from its real life cousins
+   * exception. A really simplified version from its real life cousins FutureTask and CompletableFuture.
-	 * FutureTask and CompletableFuture.
    *
    * @see java.util.concurrent.FutureTask
    * @see java.util.concurrent.CompletableFuture
@@ -70,10 +69,11 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
     }
 
     /**
-		 * Sets the value from successful execution and executes callback if available. Notifies
+     * Sets the value from successful execution and executes callback if available. Notifies any thread waiting for
-		 * any thread waiting for completion.
+     * completion.
      *
-		 * @param value value of the evaluated task
+     * @param value
+     *          value of the evaluated task
      */
     void setValue(T value) {
       this.value = value;
@@ -85,10 +85,11 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
     }
 
     /**
-		 * Sets the exception from failed execution and executes callback if available. Notifies
+     * Sets the exception from failed execution and executes callback if available. Notifies any thread waiting for
-		 * any thread waiting for completion.
+     * completion.
      *
-		 * @param exception exception of the failed task
+     * @param exception
+     *          exception of the failed task
      */
     void setException(Exception exception) {
       this.exception = exception;
@@ -101,7 +102,7 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
 
     @Override
     public boolean isCompleted() {
-			return (state > RUNNING);
+      return state > RUNNING;
     }
 
     @Override

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

@@ -14,5 +14,4 @@ public class AppTest {
     String[] args = {};
     App.main(args);
   }
-
 }

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

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

bridge/index.md

@@ -4,9 +4,14 @@ title: Bridge
 folder: bridge
 permalink: /patterns/bridge/
 categories: Structural
-tags: Java
+tags:
+ - Java
+ - Gang Of Four
+ - Difficulty-Intermediate
 ---
 
+**Also known as:** Handle/Body
+
 **Intent:** Decouple an abstraction from its implementation so that the two can
 vary independently.
 
@@ -20,3 +25,7 @@ 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

@@ -1,12 +1,11 @@
 <?xml version="1.0"?>
-<project
+<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"
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <modelVersion>4.0.0</modelVersion>
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>bridge</artifactId>
   <dependencies>
@@ -15,5 +14,10 @@
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

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

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

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

@@ -34,5 +34,4 @@ public class BlindingMagicWeapon extends MagicWeapon {
   public void blind() {
     getImp().blindImp();
   }
-
 }

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

@@ -24,8 +24,6 @@ public class Excalibur extends BlindingMagicWeaponImpl {
 
   @Override
   public void blindImp() {
-		System.out
+    System.out.println("bright light streams from Excalibur blinding the enemy");
-				.println("bright light streams from Excalibur blinding the enemy");
   }
-
 }

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

@@ -22,5 +22,4 @@ public abstract class MagicWeapon {
   public MagicWeaponImpl getImp() {
     return imp;
   }
-
 }

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

@@ -24,8 +24,6 @@ public class Mjollnir extends FlyingMagicWeaponImpl {
 
   @Override
   public void flyImp() {
-		System.out
+    System.out.println("Mjollnir hits the enemy in the air and returns back to the owner's hand");
-				.println("Mjollnir hits the enemy in the air and returns back to the owner's hand");
   }
-
 }

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

@@ -26,5 +26,4 @@ public class Stormbringer extends SoulEatingMagicWeaponImpl {
   public void eatSoulImp() {
     System.out.println("Stormbringer devours the enemy's soul");
   }
-
 }

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

@@ -2,8 +2,6 @@ package com.iluwatar.bridge;
 
 import org.junit.Test;
 
-import com.iluwatar.bridge.App;
-
 /**
  * 
  * Application test

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

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

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

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

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

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

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

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

builder/index.md

@@ -4,7 +4,10 @@ title: Builder
 folder: builder
 permalink: /patterns/builder/
 categories: Creational
-tags: Java
+tags:
+ - Java
+ - Gang Of Four
+ - Difficulty-Intermediate
 ---
 
 **Intent:** Separate the construction of a complex object from its
@@ -22,3 +25,7 @@ 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

@@ -1,12 +1,11 @@
 <?xml version="1.0"?>
-<project
+<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"
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <modelVersion>4.0.0</modelVersion>
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>builder</artifactId>
   <dependencies>

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

@@ -4,38 +4,51 @@ import com.iluwatar. builder.Hero.HeroBuilder;
 
 /**
  * 
- * This is the Builder pattern variation as described by Joshua Bloch in
+ * The intention of the Builder pattern is to find a solution to the telescoping constructor
- * Effective Java 2nd Edition.
+ * 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
+ * The Builder pattern has another benefit. It can be used for objects that contain flat data (html
- * many parameters needed. To aid the user we introduce {@link HeroBuilder} class.
+ * code, SQL query, X.509 certificate...), that is to say, data that can't be easily edited. This
- * {@link HeroBuilder} takes the minimum parameters to build {@link Hero} object in its
+ * type of data cannot be edited step by step and must be edited at once. The best way to construct
- * constructor. After that additional configuration for the {@link Hero} object can be
+ * such an object is to use a builder class.
- * done using the fluent {@link HeroBuilder} interface. When configuration is ready the
+ * <p>
- * build method is called to receive the final {@link Hero} object.
+ * 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) {
 
-		Hero mage = new HeroBuilder(Profession.MAGE, "Riobard")
+    Hero mage =
-				.withHairColor(HairColor.BLACK).withWeapon(Weapon.DAGGER)
+        new HeroBuilder(Profession.MAGE, "Riobard").withHairColor(HairColor.BLACK)
-				.build();
+            .withWeapon(Weapon.DAGGER).build();
     System.out.println(mage);
 
-		Hero warrior = new HeroBuilder(Profession.WARRIOR, "Amberjill")
+    Hero warrior =
-				.withHairColor(HairColor.BLOND)
+        new HeroBuilder(Profession.WARRIOR, "Amberjill").withHairColor(HairColor.BLOND)
-				.withHairType(HairType.LONG_CURLY).withArmor(Armor.CHAIN_MAIL)
+            .withHairType(HairType.LONG_CURLY).withArmor(Armor.CHAIN_MAIL).withWeapon(Weapon.SWORD)
-				.withWeapon(Weapon.SWORD).build();
+            .build();
     System.out.println(warrior);
 
-		Hero thief = new HeroBuilder(Profession.THIEF, "Desmond")
+    Hero thief =
-				.withHairType(HairType.BALD).withWeapon(Weapon.BOW).build();
+        new HeroBuilder(Profession.THIEF, "Desmond").withHairType(HairType.BALD)
+            .withWeapon(Weapon.BOW).build();
     System.out.println(thief);
 
   }

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

@@ -7,7 +7,8 @@ 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;
 

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

@@ -93,10 +93,12 @@ public class Hero {
     private Armor armor;
     private Weapon weapon;
 
+    /**
+     * Constructor
+     */
     public HeroBuilder(Profession profession, String name) {
       if (profession == null || name == null) {
-				throw new IllegalArgumentException(
+        throw new IllegalArgumentException("profession and name can not be null");
-						"profession and name can not be null");
       }
       this.profession = profession;
       this.name = name;

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

@@ -13,5 +13,4 @@ public enum Profession {
   public String toString() {
     return name().toLowerCase();
   }
-
 }

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

@@ -13,5 +13,4 @@ public enum Weapon {
   public String toString() {
     return name().toLowerCase();
   }
-
 }

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

@@ -2,8 +2,6 @@ package com.iluwatar.builder;
 
 import org.junit.Test;
 
-import com.iluwatar. builder.App;
-
 /**
  * 
  * Application test

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

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

business-delegate/index.md

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

business-delegate/pom.xml

@@ -6,7 +6,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+		<version>1.9.0</version>
 	</parent>
 	<artifactId>business-delegate</artifactId>
 	<dependencies>
@@ -15,5 +15,10 @@
 			<artifactId>junit</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.mockito</groupId>
+			<artifactId>mockito-core</artifactId>
+			<scope>test</scope>
+		</dependency>
 	</dependencies>
 </project>

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

@@ -1,29 +1,34 @@
 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.
+ * <p>Some of the services the Business Delegate uses are instantiated directly, and some can be
- * By using the pattern we gain loose coupling between the tiers. The Business Delegate encapsulates
+ * retrieved through service lookups. The Business Delegate itself may contain business logic too
- * knowledge about how to locate, connect to, and interact with the business objects that make up
+ * potentially tying together multiple service calls, exception handling, retrying etc.
- * 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>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
+   * Program entry point.
+   *
    * @param args command line args
    */
   public static void main(String[] args) {
 
     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);

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

@@ -1,16 +1,18 @@
 package com.iluwatar.business.delegate;
 
 /**
- * 
  * BusinessDelegate separates the presentation and business tiers
- *
  */
 public class BusinessDelegate {
 
-	private BusinessLookup lookupService = new BusinessLookup();
+  private BusinessLookup lookupService;
   private BusinessService businessService;
   private ServiceType serviceType;
 
+  public void setLookupService(BusinessLookup businessLookup) {
+    this.lookupService = businessLookup;
+  }
+
   public void setServiceType(ServiceType serviceType) {
     this.serviceType = serviceType;
   }

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 {
 
+  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 new EjbService();
+      return ejbService;
     } else {
-			return new JmsService();
+      return jmsService;
     }
   }
+
+  public void setJmsService(JmsService jmsService) {
+    this.jmsService = jmsService;
+  }
+
+  public void setEjbService(EjbService ejbService) {
+    this.ejbService = ejbService;
+  }
 }

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 +1,26 @@
+---
+layout: pattern
+title: Caching
+folder: caching
+permalink: /patterns/caching/
+categories: Other
+tags:
+ - Java
+ - Difficulty-Intermediate
+ - Performance
+---
+
+**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>1.9.0</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());
+    AppManager.find("001");
+    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());
+    AppManager.find("002");
+    System.out.println(AppManager.printCacheContent());
+    userAccount2 = AppManager.find("002");
+    userAccount2.setUserName("Jane G.");
+    AppManager.save(userAccount2);
+    System.out.println(AppManager.printCacheContent());
+    AppManager.find("002");
+    System.out.println(AppManager.printCacheContent());
+    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());
+    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());
+    AppManager.find("004");
+    System.out.println(AppManager.printCacheContent());
+  }
+}

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

@@ -0,0 +1,87 @@
+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;
+
+  private AppManager() {
+  }
+
+  /**
+   *
+   * Developer/Tester is able to choose whether the application should use MongoDB as its underlying
+   * data storage or a simple Java data structure to (temporarily) store the data/objects during
+   * runtime.
+   */
+  public static void initDb(boolean useMongoDb) {
+    if (useMongoDb) {
+      try {
+        DbManager.connect();
+      } catch (ParseException e) {
+        e.printStackTrace();
+      }
+    } else {
+      DbManager.createVirtualDb();
+    }
+  }
+
+  /**
+   * Initialize caching policy
+   */
+  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);
+  }
+
+  /**
+   * Find user account
+   */
+  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;
+  }
+
+  /**
+   * Save user account
+   */
+  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 +1,134 @@
+package com.iluwatar.caching;
+
+import java.util.ArrayList;
+
+/**
+ *
+ * The caching strategies are implemented in this class.
+ *
+ */
+public class CacheStore {
+
+  static LruCache cache = null;
+
+  private CacheStore() {
+  }
+
+  /**
+   * Init cache capacity
+   */
+  public static void initCapacity(int capacity) {
+    if (null == cache) {
+      cache = new LruCache(capacity);
+    } else {
+      cache.setCapacity(capacity);
+    }
+  }
+
+  /**
+   * Get user account using read-through cache
+   */
+  public static UserAccount readThrough(String userId) {
+    if (cache.contains(userId)) {
+      System.out.println("# Cache Hit!");
+      return cache.get(userId);
+    }
+    System.out.println("# Cache Miss!");
+    UserAccount userAccount = DbManager.readFromDb(userId);
+    cache.set(userId, userAccount);
+    return userAccount;
+  }
+
+  /**
+   * Get user account using write-through cache
+   */
+  public static void writeThrough(UserAccount userAccount) {
+    if (cache.contains(userAccount.getUserId())) {
+      DbManager.updateDb(userAccount);
+    } else {
+      DbManager.writeToDb(userAccount);
+    }
+    cache.set(userAccount.getUserId(), userAccount);
+  }
+
+  /**
+   * Get user account using write-around cache
+   */
+  public static void writeAround(UserAccount userAccount) {
+    if (cache.contains(userAccount.getUserId())) {
+      DbManager.updateDb(userAccount);
+      cache.invalidate(userAccount.getUserId()); // Cache data has been updated -- remove older
+                                                 // version from cache.
+    } else {
+      DbManager.writeToDb(userAccount);
+    }
+  }
+
+  /**
+   * Get user account using read-through cache with write-back policy
+   */
+  public static UserAccount readThroughWithWriteBackPolicy(String userId) {
+    if (cache.contains(userId)) {
+      System.out.println("# Cache Hit!");
+      return cache.get(userId);
+    }
+    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;
+  }
+
+  /**
+   * Set user account
+   */
+  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);
+  }
+
+  /**
+   * Clears cache
+   */
+  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);
+    }
+  }
+
+  /**
+   * Print user accounts
+   */
+  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 +1,143 @@
+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;
+
+  private DbManager() {
+  }
+
+  /**
+   * Create DB
+   */
+  public static void createVirtualDb() {
+    useMongoDB = false;
+    virtualDB = new HashMap<String, UserAccount>();
+  }
+
+  /**
+   * Connect to DB
+   */
+  public static void connect() throws ParseException {
+    useMongoDB = true;
+    mongoClient = new MongoClient();
+    db = mongoClient.getDatabase("test");
+  }
+
+  /**
+   * Read user account from DB
+   */
+  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;
+  }
+
+  /**
+   * Write user account to DB
+   */
+  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()));
+  }
+
+  /**
+   * Update DB
+   */
+  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 +1,163 @@
+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;
+  }
+
+  /**
+   * Get user account
+   */
+  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;
+    }
+  }
+
+  /**
+   * Set user account
+   */
+  public void set(String userId, UserAccount userAccount) {
+    if (cache.containsKey(userId)) {
+      Node old = cache.get(userId);
+      old.userAccount = userAccount;
+      remove(old);
+      setHead(old);
+    } else {
+      Node newNode = new Node(userId, userAccount);
+      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);
+  }
+
+  /**
+   * Invalidate cache for user
+   */
+  public void invalidate(String userId) {
+    System.out.println("# " + userId + " has been updated! Removing older version from cache...");
+    Node toBeRemoved = cache.get(userId);
+    remove(toBeRemoved);
+    cache.remove(userId);
+  }
+
+  public boolean isFull() {
+    return cache.size() >= capacity;
+  }
+
+  public UserAccount getLruData() {
+    return end.userAccount;
+  }
+
+  /**
+   * Clear cache
+   */
+  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;
+  }
+
+  /**
+   * Set cache capacity
+   */
+  public void setCapacity(int newCapacity) {
+    if (capacity > newCapacity) {
+      clear(); // Behavior can be modified to accommodate for decrease in cache size. For now, we'll
+               // just clear the cache.
+    } else {
+      this.capacity = newCapacity;
+    }
+  }
+}

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

@@ -0,0 +1,50 @@
+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;
+
+  /**
+   * Constructor
+   */
+  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/index.md

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

callback/pom.xml

@@ -1,12 +1,11 @@
 <?xml version="1.0"?>
-<project
+<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"
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <modelVersion>4.0.0</modelVersion>
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>callback</artifactId>
   <dependencies>

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

@@ -2,12 +2,16 @@ package com.iluwatar.callback;
 
 /**
  * 
- * Callback pattern is more native for functional languages where functions are treated as first-class citizens.
+ * Callback pattern is more native for functional languages where functions are treated as
- * Prior to Java 8 callbacks can be simulated using simple (alike command) interfaces.
+ * first-class citizens. Prior to Java 8 callbacks can be simulated using simple (alike command)
+ * interfaces.
  * 
  */
 public class App {
 
+  /**
+   * Program entry point
+   */
   public static void main(String[] args) {
     Task task = new SimpleTask();
     Callback callback = new Callback() {

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

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

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

@@ -9,7 +9,6 @@ public class SimpleTask extends Task {
 
   @Override
   public void execute() {
-		System.out.println("Perform some important activity.");
+    System.out.println("Perform some important activity and after call the callback method.");
   }
-
 }

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

@@ -7,6 +7,9 @@ package com.iluwatar.callback;
  */
 public abstract class Task {
 
+  /**
+   * Execute with callback
+   */
   public final void executeWith(Callback callback) {
     execute();
     if (callback != null) {

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;
 
 /**
+ * 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.
  *
- * Application test
+ * Could be done with mock objects as well where the call method call is verified.
- *
  */
 public class AppTest {
 
+  private Integer callingCount = 0;
+
   @Test
   public void test() {
-		String[] args = {};
+    Callback callback = new Callback() {
-		App.main(args);
+      @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 +4,10 @@ title: Chain of responsibility
 folder: chain
 permalink: /patterns/chain/
 categories: Behavioral
-tags: Java
+tags:
+ - Java
+ - Gang Of Four
+ - Difficulty-Intermediate
 ---
 
 **Intent:** Avoid coupling the sender of a request to its receiver by giving
@@ -23,3 +26,7 @@ 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

@@ -1,12 +1,11 @@
 <?xml version="1.0"?>
-<project
+<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"
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <modelVersion>4.0.0</modelVersion>
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>chain</artifactId>
   <dependencies>

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

@@ -2,24 +2,29 @@ package com.iluwatar.chain;
 
 /**
  * 
- * Chain of Responsibility organizes request handlers ({@link RequestHandler}) into a
+ * The Chain of Responsibility pattern is a design pattern consisting of command objects and a
- * chain where each handler has a chance to act on the request on its turn. In
+ * series of processing objects. Each processing object contains logic that defines the types of
- * this example the king ({@link OrcKing}) makes requests and the military orcs
+ * command objects that it can handle; the rest are passed to the next processing object in the
- * ({@link OrcCommander}, {@link OrcOfficer}, {@link OrcSoldier}) form the handler chain.
+ * 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) {
 
     OrcKing king = new OrcKing();
     king.makeRequest(new Request(RequestType.DEFEND_CASTLE, "defend castle"));
-		king.makeRequest(new Request(RequestType.TORTURE_PRISONER,
+    king.makeRequest(new Request(RequestType.TORTURE_PRISONER, "torture prisoner"));
-				"torture prisoner"));
     king.makeRequest(new Request(RequestType.COLLECT_TAX, "collect tax"));
 
   }

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

@@ -15,6 +15,7 @@ public class OrcCommander extends RequestHandler {
   public void handleRequest(Request req) {
     if (req.getRequestType().equals(RequestType.DEFEND_CASTLE)) {
       printHandling(req);
+      req.markHandled();
     } else {
       super.handleRequest(req);
     }

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

@@ -15,6 +15,7 @@ public class OrcOfficer extends RequestHandler {
   public void handleRequest(Request req) {
     if (req.getRequestType().equals(RequestType.TORTURE_PRISONER)) {
       printHandling(req);
+      req.markHandled();
     } else {
       super.handleRequest(req);
     }

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

@@ -15,6 +15,7 @@ public class OrcSoldier extends RequestHandler {
   public void handleRequest(Request req) {
     if (req.getRequestType().equals(RequestType.COLLECT_TAX)) {
       printHandling(req);
+      req.markHandled();
     } else {
       super.handleRequest(req);
     }

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

@@ -1,38 +1,78 @@
 package com.iluwatar.chain;
 
+import java.util.Objects;
+
 /**
- * 
  * Request
- *
  */
 public class Request {
 
-	private String requestDescription;
+  /**
-	private RequestType requestType;
+   * The type of this request, used by each item in the chain to see if they should or can handle
+   * this particular request
+   */
+  private final RequestType requestType;
 
-	public Request(RequestType requestType, String requestDescription) {
+  /**
-		this.setRequestType(requestType);
+   * A description of the request
-		this.setRequestDescription(requestDescription);
+   */
+  private final String requestDescription;
+
+  /**
+   * Indicates if the request is handled or not. A request can only switch state from unhandled to
+   * handled, there's no way to 'unhandle' a request
+   */
+  private boolean handled = false;
+
+  /**
+   * Create a new request of the given type and accompanied description.
+   *
+   * @param requestType        The type of request
+   * @param requestDescription The description of the request
+   */
+  public Request(final RequestType requestType, final String requestDescription) {
+    this.requestType = Objects.requireNonNull(requestType);
+    this.requestDescription = Objects.requireNonNull(requestDescription);
   }
 
+  /**
+   * Get a description of the request
+   *
+   * @return A human readable description of the request
+   */
   public String getRequestDescription() {
     return requestDescription;
   }
 
-	public void setRequestDescription(String requestDescription) {
+  /**
-		this.requestDescription = requestDescription;
+   * Get the type of this request, used by each person in the chain of command to see if they should
-	}
+   * or can handle this particular request
-
+   *
+   * @return The request type
+   */
   public RequestType getRequestType() {
     return requestType;
   }
 
-	public void setRequestType(RequestType requestType) {
+  /**
-		this.requestType = requestType;
+   * Mark the request as handled
+   */
+  public void markHandled() {
+    this.handled = true;
+  }
+
+  /**
+   * Indicates if this request is handled or not
+   *
+   * @return <tt>true</tt> when the request is handled, <tt>false</tt> if not
+   */
+  public boolean isHandled() {
+    return this.handled;
   }
 
   @Override
   public String toString() {
     return getRequestDescription();
   }
+
 }

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

@@ -13,6 +13,9 @@ public abstract class RequestHandler {
     this.next = next;
   }
 
+  /**
+   * Request handler
+   */
   public void handleRequest(Request req) {
     if (next != null) {
       next.handleRequest(req);

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

@@ -2,8 +2,6 @@ package com.iluwatar.chain;
 
 import org.junit.Test;
 
-import com.iluwatar.chain.App;
-
 /**
  * 
  * Application test

chain/src/test/java/com/iluwatar/chain/OrcKingTest.java

@@ -0,0 +1,37 @@
+package com.iluwatar.chain;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Date: 12/6/15 - 9:29 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class OrcKingTest {
+
+  /**
+   * All possible requests
+   */
+  private static final Request[] REQUESTS = new Request[]{
+      new Request(RequestType.DEFEND_CASTLE, "Don't let the barbarians enter my castle!!"),
+      new Request(RequestType.TORTURE_PRISONER, "Don't just stand there, tickle him!"),
+      new Request(RequestType.COLLECT_TAX, "Don't steal, the King hates competition ..."),
+  };
+
+  @Test
+  public void testMakeRequest() throws Exception {
+    final OrcKing king = new OrcKing();
+
+    for (final Request request : REQUESTS) {
+      king.makeRequest(request);
+      assertTrue(
+          "Expected all requests from King to be handled, but [" + request + "] was not!",
+          request.isHandled()
+      );
+    }
+
+  }
+
+}

checkstyle-suppressions.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE suppressions PUBLIC "-//Puppy Crawl//DTD Suppressions 1.1//EN"
+    "http://www.puppycrawl.com/dtds/suppressions_1_1.dtd">
+<suppressions>
+   <suppress checks="AvoidStarImport" files="[\\/]src[\\/]test[\\/]java[\\/]"/>
+   <suppress checks="[a-zA-Z0-9]*" files="[\\/]src[\\/]test[\\/]resources[\\/]"/>
+   <suppress checks="[a-zA-Z0-9]*" files="[\\/]build[\\/]generated-sources[\\/]"/>
+   <suppress checks="[a-zA-Z0-9]*" files="[\\/]src[\\/]main[\\/]resources[\\/]"/>
+</suppressions>

checkstyle.xml

@@ -26,7 +26,9 @@
 <module name="Checker">
     <property name="charset" value="UTF-8"/>
 	
-    <property name="severity" value="warning"/>
+	<property name="fileExtensions" value="java, xml, properties"/>
+
+    <property name="severity" value="error"/>
 
     <!-- Checks for whitespace                               -->
     <!-- See http://checkstyle.sf.net/config_whitespace.html -->
@@ -48,7 +50,7 @@
             <property name="allowNonPrintableEscapes" value="true"/>
         </module>
         <module name="LineLength">
-            <property name="max" value="100"/>
+            <property name="max" value="120"/>
             <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
         </module>
         <module name="AvoidStarImport"/>
@@ -61,7 +63,7 @@
         </module>
         <module name="NeedBraces"/>
         <module name="LeftCurly">
-            <property name="maxLineLength" value="100"/>
+            <property name="maxLineLength" value="120"/>
         </module>
         <module name="RightCurly"/>
         <module name="RightCurly">
@@ -86,9 +88,6 @@
         <module name="FallThrough"/>
         <module name="UpperEll"/>
         <module name="ModifierOrder"/>
-        <module name="EmptyLineSeparator">
-            <property name="allowNoEmptyLineBetweenFields" value="true"/>
-        </module>
         <module name="SeparatorWrap">
             <property name="tokens" value="DOT"/>
             <property name="option" value="nl"/>
@@ -97,42 +96,19 @@
             <property name="tokens" value="COMMA"/>
             <property name="option" value="EOL"/>
         </module>
-        <module name="PackageName">
+		
-            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
+        <!-- Checks for Naming Conventions.                  -->
-            <message key="name.invalidPattern"
+        <!-- See http://checkstyle.sf.net/config_naming.html -->
-                     value="Package name ''{0}'' must match pattern ''{1}''."/>
+        <module name="ConstantName"/>
-        </module>
+        <module name="LocalFinalVariableName"/>
-        <module name="TypeName">
+        <module name="LocalVariableName"/>
-            <message key="name.invalidPattern"
+        <module name="MemberName"/>
-                     value="Type name ''{0}'' must match pattern ''{1}''."/>
+        <module name="MethodName"/>
-        </module>
+        <module name="PackageName"/>
-        <module name="MemberName">
+        <module name="ParameterName"/>
-            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$"/>
+        <module name="StaticVariableName"/>
-            <message key="name.invalidPattern"
+        <module name="TypeName"/>
-                     value="Member name ''{0}'' must match pattern ''{1}''."/>
+
-        </module>
-        <module name="ParameterName">
-            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$"/>
-            <message key="name.invalidPattern"
-                     value="Parameter name ''{0}'' must match pattern ''{1}''."/>
-        </module>
-        <module name="LocalVariableName">
-            <property name="tokens" value="VARIABLE_DEF"/>
-            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$"/>
-            <property name="allowOneCharVarInForLoop" value="true"/>
-            <message key="name.invalidPattern"
-                     value="Local variable name ''{0}'' must match pattern ''{1}''."/>
-        </module>
-        <module name="ClassTypeParameterName">
-            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
-            <message key="name.invalidPattern"
-                     value="Class type name ''{0}'' must match pattern ''{1}''."/>
-        </module>
-        <module name="MethodTypeParameterName">
-            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
-            <message key="name.invalidPattern"
-                     value="Method type name ''{0}'' must match pattern ''{1}''."/>
-        </module>
         <module name="NoFinalizer"/>
         <module name="GenericWhitespace">
             <message key="ws.followed"
@@ -157,14 +133,6 @@
             <property name="allowedAbbreviationLength" value="1"/>
         </module>
         <module name="OverloadMethodsDeclarationOrder"/>
-        <module name="VariableDeclarationUsageDistance"/>
-        <module name="CustomImportOrder">
-            <property name="thirdPartyPackageRegExp" value=".*"/>
-            <property name="specialImportsRegExp" value="com.google"/>
-            <property name="sortImportsInGroupAlphabetically" value="true"/>
-            <property name="customImportOrderRules"
-                      value="STATIC###SPECIAL_IMPORTS###THIRD_PARTY_PACKAGE###STANDARD_JAVA_PACKAGE"/>
-        </module>
         <module name="MethodParamPad"/>
         <module name="OperatorWrap">
             <property name="option" value="NL"/>
@@ -180,11 +148,6 @@
         </module>
         <module name="NonEmptyAtclauseDescription"/>
         <module name="JavadocTagContinuationIndentation"/>
-        <module name="SummaryJavadocCheck">
-            <property name="forbiddenSummaryFragments"
-                      value="^@return the *|^This method returns |^A [{]@code [a-zA-Z0-9]+[}]( is a )"/>
-        </module>
-        <module name="JavadocParagraph"/>
         <module name="AtclauseOrder">
             <property name="tagOrder" value="@param, @return, @throws, @deprecated"/>
             <property name="target" value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF, VARIABLE_DEF"/>
@@ -195,7 +158,7 @@
             <property name="allowMissingThrowsTags" value="true"/>
             <property name="allowMissingReturnTag" value="true"/>
             <property name="minLineCount" value="2"/>
-            <property name="allowedAnnotations" value="Override, Test"/>
+            <property name="allowedAnnotations" value="Override, Test, Before, After, Parameters, Given, When, BeforeClass, AfterClass, Parameterized"/>
             <property name="allowThrowsTagsForSubclasses" value="true"/>
         </module>
         <module name="MethodName">
@@ -205,4 +168,5 @@
         </module>
         <module name="SingleLineJavadoc"/>
     </module>
+
 </module>

command/index.md

@@ -4,9 +4,14 @@ title: Command
 folder: command
 permalink: /patterns/command/
 categories: Behavioral
-tags: Java
+tags: 
+ - Java
+ - Gang Of Four
+ - Difficulty-Intermediate
 ---
 
+**Also known as:** Action, Transaction
+
 **Intent:** Encapsulate a request as an object, thereby letting you
 parameterize clients with different requests, queue or log requests, and
 support undoable operations.
@@ -30,3 +35,7 @@ support undoable operations.
 **Real world examples:**
 
 * [java.lang.Runnable](http://docs.oracle.com/javase/8/docs/api/java/lang/Runnable.html)
+
+**Credits**
+
+* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)

command/pom.xml

@@ -1,12 +1,11 @@
 <?xml version="1.0"?>
-<project
+<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"
-	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <modelVersion>4.0.0</modelVersion>
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-		<version>1.6.0</version>
+    <version>1.9.0</version>
   </parent>
   <artifactId>command</artifactId>
   <dependencies>
@@ -15,5 +14,10 @@
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

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

@@ -2,19 +2,22 @@ package com.iluwatar.command;
 
 /**
  * 
- * In Command pattern actions are objects that can be executed and undone. 
+ * The Command pattern is a behavioral design pattern in which an object is used to encapsulate all
+ * information needed to perform an action or trigger an event at a later time. This information
+ * includes the method name, the object that owns the method and values for the method parameters.
  * <p>
- * Four terms always associated with the command pattern are command, receiver, invoker and client. A command 
+ * Four terms always associated with the command pattern are command, receiver, invoker and client.
- * object (spell) knows about the receiver (target) and invokes a method of the receiver. Values for parameters of 
+ * A command object (spell) knows about the receiver (target) and invokes a method of the receiver.
- * the receiver method are stored in the command. The receiver then does the work. An invoker object (wizard) 
+ * Values for parameters of the receiver method are stored in the command. The receiver then does
- * knows how to execute a command, and optionally does bookkeeping about the command execution. The invoker 
+ * the work. An invoker object (wizard) knows how to execute a command, and optionally does
- * does not know anything about a concrete command, it knows only about command interface. Both an invoker object 
+ * bookkeeping about the command execution. The invoker does not know anything about a concrete
- * and several command objects are held by a client object (app). The client decides which commands to execute at 
+ * command, it knows only about command interface. Both an invoker object and several command
- * which points. To execute a command, it passes the command object to the invoker object.
+ * objects are held by a client object (app). The client decides which commands to execute at which
+ * points. To execute a command, it passes the command object to the invoker object.
  * <p>
- * In other words, in this example the wizard casts spells on the goblin. The wizard keeps track of the previous
+ * In other words, in this example the wizard casts spells on the goblin. The wizard keeps track of
- * spells cast, so it is easy to undo them. In addition, the wizard keeps track of the spells undone, so they
+ * the previous spells cast, so it is easy to undo them. In addition, the wizard keeps track of the
- * can be redone.
+ * spells undone, so they can be redone.
  * 
  * 
  */
@@ -22,6 +25,7 @@ public class App {
 
   /**
    * Program entry point
+   * 
    * @param args command line args
    */
   public static void main(String[] args) {

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

@@ -30,9 +30,12 @@ public abstract class Target {
   @Override
   public abstract String toString();
 
+  /**
+   * Print status
+   */
   public void printStatus() {
-		System.out.println(String.format("%s, [size=%s] [visibility=%s]", this,
+    System.out.println(String.format("%s, [size=%s] [visibility=%s]", this, getSize(),
-				getSize(), getVisibility()));
+        getVisibility()));
     System.out.println();
   }
 }

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

@@ -13,15 +13,20 @@ public class Wizard {
   private Deque<Command> undoStack = new LinkedList<>();
   private Deque<Command> redoStack = new LinkedList<>();
 
-	public Wizard() {
+  public Wizard() {}
-	}
 
+  /**
+   * Cast spell
+   */
   public void castSpell(Command command, Target target) {
     System.out.println(this + " casts " + command + " at " + target);
     command.execute(target);
     undoStack.offerLast(command);
   }
 
+  /**
+   * Undo last spell
+   */
   public void undoLastSpell() {
     if (!undoStack.isEmpty()) {
       Command previousSpell = undoStack.pollLast();
@@ -31,6 +36,9 @@ public class Wizard {
     }
   }
 
+  /**
+   * Redo last spell
+   */
   public void redoLastSpell() {
     if (!redoStack.isEmpty()) {
       Command previousSpell = redoStack.pollLast();