added command sample

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

@@ -0,0 +1,31 @@
+package com.iluwatar;
+
+public class Wizard extends Target {
+
+	private Command previousSpell;
+	
+	public Wizard() {
+		this.setSize(Size.NORMAL);
+		this.setVisibility(Visibility.VISIBLE);
+		previousSpell = null;
+	}
+	
+	public void castSpell(Command command, Target target) {
+		System.out.println(this + " casts " + command + " at " + target);
+		command.execute(target);
+		previousSpell = command;
+	}
+
+	public void undoLastSpell() {
+		if (previousSpell != null) {
+			System.out.println(this + " undoes " + previousSpell);
+			previousSpell.undo();
+		}
+	}
+	
+	@Override
+	public String toString() {
+		return "Wizard";
+	}
+	
+}