Changed package naming across all examples.

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

@@ -0,0 +1,36 @@
+package com.iluwatar.command;
+
+/**
+ * 
+ * In Command pattern actions are objects that can be executed and undone. 
+ * 
+ * In this example the commands are the spells cast by the wizard on the goblin.
+ * 
+ */
+public class App {
+
+	public static void main(String[] args) {
+		Wizard wizard = new Wizard();
+		Goblin goblin = new Goblin();
+
+		goblin.printStatus();
+
+		wizard.castSpell(new ShrinkSpell(), goblin);
+		goblin.printStatus();
+
+		wizard.castSpell(new InvisibilitySpell(), goblin);
+		goblin.printStatus();
+
+		wizard.undoLastSpell();
+		goblin.printStatus();
+
+		wizard.undoLastSpell();
+		goblin.printStatus();
+
+		wizard.redoLastSpell();
+		goblin.printStatus();
+
+		wizard.redoLastSpell();
+		goblin.printStatus();
+	}
+}

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

@@ -0,0 +1,19 @@
+package com.iluwatar.command;
+
+/**
+ * 
+ * Interface for Commands.
+ * 
+ */
+public abstract class Command {
+
+	public abstract void execute(Target target);
+
+	public abstract void undo();
+
+	public abstract void redo();
+
+	@Override
+	public abstract String toString();
+
+}

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

@@ -0,0 +1,15 @@
+package com.iluwatar.command;
+
+public class Goblin extends Target {
+
+	public Goblin() {
+		setSize(Size.NORMAL);
+		setVisibility(Visibility.VISIBLE);
+	}
+
+	@Override
+	public String toString() {
+		return "Goblin";
+	}
+
+}

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

@@ -0,0 +1,31 @@
+package com.iluwatar.command;
+
+public class InvisibilitySpell extends Command {
+
+	private Target target;
+
+	@Override
+	public void execute(Target target) {
+		target.setVisibility(Visibility.INVISIBLE);
+		this.target = target;
+	}
+
+	@Override
+	public void undo() {
+		if (target != null) {
+			target.setVisibility(Visibility.VISIBLE);
+		}
+	}
+
+	@Override
+	public void redo() {
+		if (target != null) {
+			target.setVisibility(Visibility.INVISIBLE);
+		}
+	}
+
+	@Override
+	public String toString() {
+		return "Invisibility spell";
+	}
+}

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

@@ -0,0 +1,33 @@
+package com.iluwatar.command;
+
+public class ShrinkSpell extends Command {
+
+	private Size oldSize;
+	private Target target;
+
+	@Override
+	public void execute(Target target) {
+		oldSize = target.getSize();
+		target.setSize(Size.SMALL);
+		this.target = target;
+	}
+
+	@Override
+	public void undo() {
+		if (oldSize != null && target != null) {
+			Size temp = target.getSize();
+			target.setSize(oldSize);
+			oldSize = temp;
+		}
+	}
+
+	@Override
+	public void redo() {
+		undo();
+	}
+
+	@Override
+	public String toString() {
+		return "Shrink spell";
+	}
+}

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

@@ -0,0 +1,22 @@
+package com.iluwatar.command;
+
+/**
+ *
+ * Enumeration for target size.
+ *
+ */
+public enum Size {
+
+    SMALL("small"), NORMAL("normal"), LARGE("large"), UNDEFINED("");
+    
+    private String title;
+
+    Size(String title) {
+        this.title = title;
+    }
+
+    @Override
+	public String toString() {
+        return title;
+	}
+}

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

@@ -0,0 +1,38 @@
+package com.iluwatar.command;
+
+/**
+ * 
+ * Base class for spell targets.
+ *
+ */
+public abstract class Target {
+
+	private Size size;
+
+	private Visibility visibility;
+
+	public Size getSize() {
+		return size;
+	}
+
+	public void setSize(Size size) {
+		this.size = size;
+	}
+
+	public Visibility getVisibility() {
+		return visibility;
+	}
+
+	public void setVisibility(Visibility visibility) {
+		this.visibility = visibility;
+	}
+
+	@Override
+	public abstract String toString();
+
+	public void printStatus() {
+		System.out.println(String.format("%s, [size=%s] [visibility=%s]", this,
+				getSize(), getVisibility()));
+		System.out.println();
+	}
+}

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

@@ -0,0 +1,22 @@
+package com.iluwatar.command;
+
+/**
+ * 
+ * Enumeration for target visibility.
+ *
+ */
+public enum Visibility {
+
+	VISIBLE("visible"), INVISIBLE("invisible"), UNDEFINED("");
+
+    private String title;
+
+    Visibility(String title) {
+        this.title = title;
+    }
+
+    @Override
+	public String toString() {
+		return title;
+	}
+}

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

@@ -0,0 +1,45 @@
+package com.iluwatar.command;
+
+import java.util.Deque;
+import java.util.LinkedList;
+
+public class Wizard extends Target {
+
+	private Deque<Command> undoStack = new LinkedList<>();
+	private Deque<Command> redoStack = new LinkedList<>();
+
+	public Wizard() {
+		setSize(Size.NORMAL);
+		setVisibility(Visibility.VISIBLE);
+	}
+
+	public void castSpell(Command command, Target target) {
+		System.out.println(this + " casts " + command + " at " + target);
+		command.execute(target);
+		undoStack.offerLast(command);
+	}
+
+	public void undoLastSpell() {
+		if (!undoStack.isEmpty()) {
+			Command previousSpell = undoStack.pollLast();
+			redoStack.offerLast(previousSpell);
+			System.out.println(this + " undoes " + previousSpell);
+			previousSpell.undo();
+		}
+	}
+
+	public void redoLastSpell() {
+		if (!redoStack.isEmpty()) {
+			Command previousSpell = redoStack.pollLast();
+			undoStack.offerLast(previousSpell);
+			System.out.println(this + " redoes " + previousSpell);
+			previousSpell.redo();
+		}
+	}
+
+	@Override
+	public String toString() {
+		return "Wizard";
+	}
+
+}