class TrafficLight{

    private String lightType;

    private static final TrafficLight GREENLIGHT = new TrafficLight("GreenLight");

    private static final TrafficLight REDLIGHT = new TrafficLight("RedLight");

    private static final TrafficLight YELLOWLIGHT = new TrafficLight("YellowLight");

    private TrafficLight(String lightType){

        this.lightType = lightType;

    }

    public static TrafficLight getInstance(String ch){

        switch(ch){

        case "GreenLight":

            return GREENLIGHT;

        case "RedLight":

            return REDLIGHT;

        case "YellowLight":

            return YELLOWLIGHT;

        default:

            return null;

        }

    }

    public String toString(){

        return this.lightType;

    }

}

public class TrafficLightDemo {

    public static void main(String[] args) {

        TrafficLight GreenLight = TrafficLight.getInstance("GreenLight");

        TrafficLight RedLight = TrafficLight.getInstance("RedLight");

        TrafficLight YellowLight = TrafficLight.getInstance("YellowLight");

        System.out.println(GreenLight);

        System.out.println(RedLight);

        System.out.println(YellowLight);

    }

}