public interface Command{
	public void turnOn();
}
abstract public class Lamp implements Command{
	boolean isOn = false;
	Mediator mediator;
	public Lamp(Mediator mediator){
		this.mediator = mediator;
	}
	public void on(){
		this.isOn = true;
	}
	public void off(){
		this.isOn = false;
	}
	abstract public void turnOn();
}
public class GreenLamp extends Lamp{
	public GreenLamp(Mediator mediator){
		super(mediator);
	}
	public void turnOn(){
		mediator.turnOnGreenLamp();
	}
	public String toString(){
		if(this.isOn)
			return "GreenLamp is on";
		return "GreenLamp is off";
	}
}
public class RedLamp extends Lamp{
	public RedLamp(Mediator mediator){
		super(mediator);
	}
	public void turnOn(){
		mediator.turnOnRedLamp();
	}
	public String toString(){
		if(this.isOn)
			return "RedLamp is on";
		return "RedLamp is off";
	}
}
public class YellowLamp extends Lamp{
	public YellowLamp(Mediator mediator){
		super(mediator);
	}
	public void turnOn(){
		mediator.turnOnYellowLamp();
	}
	public String toString(){
		if(this.isOn)
			return "YellowLamp is on";
		return "YellowLamp is off";
	}
}
public class Mediator{
	Lamp yLamp,gLamp,rLamp;
	public void turnOnYellowLamp(){
		yLamp.on();
		gLamp.off();
		rLamp.off();
	}
	public void turnOnGreenLamp(){
		yLamp.off();
		gLamp.on();
		rLamp.off();
	}
	public void turnOnRedLamp(){
		yLamp.off();
		gLamp.off();
		rLamp.on();
	}
	public void selectYellowLamp(YellowLamp yLamp){
		this.yLamp = yLamp;
	}
	public void selectGreenLamp(GreenLamp gLamp){
		this.gLamp = gLamp;
	}
	public void selectRedLamp(RedLamp rLamp){
		this.rLamp = rLamp;
	}
}
public class MediatorDemo {
	public static void main(String \[\]args){
		Mediator m = new Mediator();
		YellowLamp yLamp = new YellowLamp(m);
		GreenLamp gLamp = new GreenLamp(m);
		RedLamp rLamp = new RedLamp(m);
		m.selectGreenLamp(gLamp);
		m.selectRedLamp(rLamp);
		m.selectYellowLamp(yLamp);
		yLamp.turnOn();
		System.out.println(yLamp);
		System.out.println(gLamp);
		System.out.println(rLamp);
		System.out.println("\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*");
		rLamp.turnOn();
		System.out.println(yLamp);
		System.out.println(gLamp);
		System.out.println(rLamp);
	}
}