added visitor pattern sample

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

@@ -0,0 +1,16 @@
+package com.iluwatar;
+
+public class App 
+{
+    public static void main( String[] args )
+    {
+
+    	Commander commander = new Commander(
+    			new Sergeant(new Soldier(), new Soldier(), new Soldier()), 
+    			new Sergeant(new Soldier(), new Soldier(), new Soldier()));
+    	commander.accept(new SoldierVisitor());
+    	commander.accept(new SergeantVisitor());
+    	commander.accept(new CommanderVisitor());
+    	
+    }
+}

visitor/src/main/java/com/iluwatar/Commander.java

@@ -0,0 +1,19 @@
+package com.iluwatar;
+
+public class Commander extends Unit {
+
+	public Commander(Unit ... children) {
+		super(children);
+	}
+
+	@Override
+	public void accept(UnitVisitor visitor) {
+		visitor.visitCommander(this);
+		super.accept(visitor);
+	}
+	
+	@Override
+	public String toString() {
+		return "commander";
+	}
+}

visitor/src/main/java/com/iluwatar/CommanderVisitor.java

@@ -0,0 +1,22 @@
+package com.iluwatar;
+
+public class CommanderVisitor implements UnitVisitor {
+
+	@Override
+	public void visitSoldier(Soldier soldier) {
+		// TODO Auto-generated method stub
+
+	}
+
+	@Override
+	public void visitSergeant(Sergeant sergeant) {
+		// TODO Auto-generated method stub
+
+	}
+
+	@Override
+	public void visitCommander(Commander commander) {
+		System.out.println("Good to see you " + commander);
+	}
+
+}

visitor/src/main/java/com/iluwatar/Sergeant.java

@@ -0,0 +1,19 @@
+package com.iluwatar;
+
+public class Sergeant extends Unit {
+
+	public Sergeant(Unit ... children) {
+		super(children);
+	}
+
+	@Override
+	public void accept(UnitVisitor visitor) {
+		visitor.visitSergeant(this);
+		super.accept(visitor);
+	}
+	
+	@Override
+	public String toString() {
+		return "sergeant";
+	}
+}

visitor/src/main/java/com/iluwatar/SergeantVisitor.java

@@ -0,0 +1,22 @@
+package com.iluwatar;
+
+public class SergeantVisitor implements UnitVisitor {
+
+	@Override
+	public void visitSoldier(Soldier soldier) {
+		// TODO Auto-generated method stub
+
+	}
+
+	@Override
+	public void visitSergeant(Sergeant sergeant) {
+		System.out.println("Hello " + sergeant);
+	}
+
+	@Override
+	public void visitCommander(Commander commander) {
+		// TODO Auto-generated method stub
+
+	}
+
+}

visitor/src/main/java/com/iluwatar/Soldier.java

@@ -0,0 +1,19 @@
+package com.iluwatar;
+
+public class Soldier extends Unit {
+
+	public Soldier(Unit ... children) {
+		super(children);
+	}
+
+	@Override
+	public void accept(UnitVisitor visitor) {
+		visitor.visitSoldier(this);
+		super.accept(visitor);
+	}
+	
+	@Override
+	public String toString() {
+		return "soldier";
+	}
+}

visitor/src/main/java/com/iluwatar/SoldierVisitor.java

@@ -0,0 +1,22 @@
+package com.iluwatar;
+
+public class SoldierVisitor implements UnitVisitor {
+
+	@Override
+	public void visitSoldier(Soldier soldier) {
+		System.out.println("Greetings " + soldier);
+	}
+
+	@Override
+	public void visitSergeant(Sergeant sergeant) {
+		// TODO Auto-generated method stub
+
+	}
+
+	@Override
+	public void visitCommander(Commander commander) {
+		// TODO Auto-generated method stub
+
+	}
+
+}

visitor/src/main/java/com/iluwatar/Unit.java

@@ -0,0 +1,16 @@
+package com.iluwatar;
+
+public abstract class Unit {
+
+	private Unit[] children;
+
+	public Unit(Unit ... children) {
+		this.children = children;
+	}
+	
+	public void accept(UnitVisitor visitor) {
+		for (Unit child: children) {
+			child.accept(visitor);
+		}
+	}
+}

visitor/src/main/java/com/iluwatar/UnitVisitor.java

@@ -0,0 +1,9 @@
+package com.iluwatar;
+
+public interface UnitVisitor {
+
+	void visitSoldier(Soldier soldier);
+	void visitSergeant(Sergeant sergeant);
+	void visitCommander(Commander commander);
+	
+}