content: package com.iluwatar.command;
  
  /**
   * 
   * In Command pattern actions are objects that can be executed and undone. 
   *
   * Four terms always associated with the command pattern are command, receiver, invoker and client. A command 
   * object (spell) knows about receiver (target) and invokes a method of the receiver. Values for parameters of 
   * the receiver method are stored in the command. The receiver then does the work. An invoker object (wizard) 
   * knows how to execute a command, and optionally does bookkeeping about the command execution. The invoker 
   * does not know anything about a concrete command, it knows only about command interface. Both an invoker object 
   * and several command 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.
   * 
   * In other words, in this example the wizard casts spells on the goblin. The wizard keeps track of the previous
   * spells cast, so it is easy to undo them. In addition, the wizard keeps track of the spells undone, so they
   * can be redone.
   * 
   * 
   */
  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();
  	}
  }
  