Command Design Pattern Example

Command.java

package com.art.head_first.homeautomation;

public interface Command {

  void execute();
  void undo();

}

Light.java

package com.art.head_first.homeautomation;

public class Light {

  boolean isOn;

  public void on(){
    isOn = true;
    System.out.println("Light is On");
  }

  public void off(){
    isOn = false;
    System.out.println("Light is Off");
  }

}

LightOffCommand.java

package com.art.head_first.homeautomation;

public class LightOffCommand implements Command{

  Light light;

  public LightOffCommand(Light light) {
    this.light = light;
  }

  @Override
  public void execute() {
    light.off();
  }

  @Override
  public void undo() {
    light.on();
  }

}

LightOnCommand.java

package com.art.head_first.homeautomation;

public class LightOnCommand implements Command{

  Light light;

  @Override
  public void execute() {
    light.on();
  }

  public LightOnCommand(Light light) {
    this.light = light;
  }

  @Override
  public void undo() {
    light.off();
  }

}

SimpleRemoteControl.java

package com.art.head_first.homeautomation;

public class SimpleRemoteControl {
  Command slot;

  public void setCommand(Command command){
    slot = command;
  }

  public void pressButton(){
    slot.execute();
  }

  public void undo(){
    slot.undo();
  }

}

SimpleRemoteControlTest.java

package com.art.head_first.homeautomation;

/**
 * Client Class is responsible for Creating Concrete Commands and setting it's receiver
 */
public class SimpleRemoteControlTest {

  public static void main(String[] args) {
    SimpleRemoteControl rc = new SimpleRemoteControl();

    Light light = new Light();
    Stereo stereo = new Stereo();

    rc.setCommand(new LightOnCommand(light));
    rc.pressButton();
    rc.undo();

    rc.setCommand(new StereoOnCommand(stereo));
    rc.pressButton();
    rc.undo();

    rc.setCommand(new StereoOffCommand(stereo));
    rc.pressButton();
    rc.undo();
  }
}

Stereo.java

package com.art.head_first.homeautomation;

public class Stereo {

  boolean isOn;
  int volume;

  public void on(){
    this.isOn = true;
    System.out.println("Stereo is On");
  }

  public void off(){
    this.isOn = false;
    System.out.println("Stereo is Off");
  }

  public void setVolume(int volume)
  {
    this.volume = volume;
    System.out.println("Stereo Volume is set to: " + volume);
  }

}

StereoOffCommand.java

package com.art.head_first.homeautomation;

public class StereoOffCommand implements Command{

  Stereo stereo;

  public StereoOffCommand(Stereo stereo) {
    this.stereo = stereo;
  }

  @Override
  public void execute() {
    stereo.off();
  }

  @Override
  public void undo() {
    stereo.on();
  }

}

StereoOnCommand.java

package com.art.head_first.homeautomation;

public class StereoOnCommand implements Command{

  Stereo stereo;

  public StereoOnCommand(Stereo stereo) {
    this.stereo = stereo;
  }

  @Override
  public void execute() {
    stereo.on();
  }

  @Override
  public void undo() {
    stereo.off();
  }

}