# 커맨드

public interface Command {
  public abstract void execute();
}

public class Button {
  private Command theCommand;
  
  public Button(Command theCommand) {
    setCommand(theCommand);
  }

  public void setCommand(Command newCommand) {
    this.theCommand = newCommand;
  }

  public void pressed() {
    theCommand.execute();
  }
}

public class Lamp {
  public void turnOn() {
    System.out.println("Lamp On");
  }
}

public class LampOnCommand implements Command {
  private Lamp theLamp;

  public LampOnCommand(Lamp theLamp) {
    this.theLamp = theLamp;
  }

  public void execute() {
    theLamp.turnOn();
  }
}

public class Alarm {
  public void start() {
    System.out.println("Alarming");
  }
}

public class AlarmStartCommand implements Command {
  private Alarm theAlarm;
  
  public AlarmStartCommand(Alarm theAlarm) {
    this.theAlarm = theAlarm;
  }

  public void execute() {
    theAlarm.start();
  }
}

public class Client {
  public static void main(String[] args) {
    Lamp lamp = new Lamp();
    Command lampOnCommand = new LampOnCommand(lamp);

    Alarm alarm = new Alarm();
    Command alarmStartCommand = new AlarmStartCommand(alarm);

    // 램프 켜는 Command 설정
    Button button1 = new Button(lampOnCommand);
    // 램프 켜는 기능 수행
    button1.pressed();

    // 알람 울리는 Command 설정
    Button button2 = new Button(alarmStartCommand);
    // 알람 울리는 기능 수행
    button2.pressed();
    // 다시 램프 켜는 Command 설정
    button2.setCommand(lampOnCommand);
    // 램프 켜는 기능 수행
    button2.pressed();
  }
}