interface Commend {

  public void execute();

}

class Light {

  public void on() {

    System.out.println("light on");

  }

  public void off() {

    System.out.println("light off");

  }

}

class LintOnCommend implements Commend {

  Light light;

  public LintOnCommend(Light light) {

    this.light = light;

  }

  @Override

  public void execute() {

    light.on();

  }

}

class SimpleRemoteControl {

  Commend commend;

  public SimpleRemoteControl() {}

  public void setCommend(Commend commend) {

    this.commend = commend;

  }

  public void buttonWasPressed() {

    commend.execute();

  }

}

public class Test {

  public static void main(String[] args) {

    SimpleRemoteControl control = new SimpleRemoteControl();

    Light light = new Light();

    LintOnCommend onCommend = new LintOnCommend(light);

    control.setCommend(onCommend);

    control.buttonWasPressed();

  }

}