added strategy pattern sample

pom.xml

@@ -38,6 +38,7 @@
     <module>memento</module>
     <module>observer</module>
     <module>state</module>
+    <module>strategy</module>
   </modules>
   
 <build>

strategy/pom.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.0-SNAPSHOT</version>
+  </parent>
+  <groupId>com.iluwatar</groupId>
+  <artifactId>strategy</artifactId>
+  <version>1.0-SNAPSHOT</version>
+  <name>strategy</name>
+  <url>http://maven.apache.org</url>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>3.8.1</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>

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

@@ -0,0 +1,17 @@
+package com.iluwatar;
+
+public class App 
+{
+    public static void main( String[] args )
+    {
+    	System.out.println("Green dragon spotted ahead!");
+    	DragonSlayer dragonSlayer = new DragonSlayer(new MeleeStrategy());
+    	dragonSlayer.goToBattle();
+    	System.out.println("Red dragon emerges.");
+    	dragonSlayer.changeStrategy(new ProjectileStrategy());
+    	dragonSlayer.goToBattle();
+    	System.out.println("Black dragon lands before you.");
+    	dragonSlayer.changeStrategy(new SpellStrategy());
+    	dragonSlayer.goToBattle();
+    }
+}

strategy/src/main/java/com/iluwatar/DragonSlayer.java

@@ -0,0 +1,18 @@
+package com.iluwatar;
+
+public class DragonSlayer {
+
+	private DragonSlayingStrategy strategy;
+
+	public DragonSlayer(DragonSlayingStrategy strategy) {
+		this.strategy = strategy;
+	}
+
+	public void changeStrategy(DragonSlayingStrategy strategy) {
+		this.strategy = strategy;
+	}
+	
+	public void goToBattle() {
+		strategy.execute();
+	}
+}

strategy/src/main/java/com/iluwatar/DragonSlayingStrategy.java

@@ -0,0 +1,7 @@
+package com.iluwatar;
+
+public interface DragonSlayingStrategy {
+
+	void execute();
+	
+}

strategy/src/main/java/com/iluwatar/MeleeStrategy.java

@@ -0,0 +1,10 @@
+package com.iluwatar;
+
+public class MeleeStrategy implements DragonSlayingStrategy {
+
+	@Override
+	public void execute() {
+		System.out.println("With your Excalibur you severe the dragon's head!");
+	}
+
+}

strategy/src/main/java/com/iluwatar/ProjectileStrategy.java

@@ -0,0 +1,10 @@
+package com.iluwatar;
+
+public class ProjectileStrategy implements DragonSlayingStrategy {
+
+	@Override
+	public void execute() {
+		System.out.println("You shoot the dragon with the magical crossbow and it falls dead on the ground!");
+	}
+
+}

strategy/src/main/java/com/iluwatar/SpellStrategy.java

@@ -0,0 +1,10 @@
+package com.iluwatar;
+
+public class SpellStrategy implements DragonSlayingStrategy {
+
+	@Override
+	public void execute() {
+		System.out.println("You cast the spell of disintegration and the dragon vaporizes in a pile of dust!");
+	}
+
+}