TrafficLightDemo

enum TrafficLightColor{
	RED, GREEN, YELLOW;
}
class TrafficLightSimulator implements Runnable{
	private TrafficLightColor tlc; // holds the traffic light color
	private boolean stop =  false; // set to true to stop the simulation
	private boolean changed = false; // true when the light has changed
	
	TrafficLightSimulator(TrafficLightColor init) {
	    tlc = init;
	}
	
	TrafficLightSimulator() {
		tlc = TrafficLightColor.RED;
	}
	public void run() {
		while(!stop) {
			try {
				switch(tlc) {
				case GREEN:
					Thread.sleep(10000);
					break;
				case YELLOW:
					Thread.sleep(2000);
					break;
				case RED:
					Thread.sleep(120000);
					break;
				}
			} catch (InterruptedException e) {
				// TODO: handle exception
				System.out.println(e);
			}
			changeColor();
		}
	}
	synchronized void changeColor() {
		switch(tlc) {
		case RED:
			tlc = TrafficLightColor.GREEN;
			break;
		case YELLOW:
			tlc = TrafficLightColor.RED;
			break;
		case GREEN:
			tlc = TrafficLightColor.YELLOW;
		}
		changed = true;
		notify();
	}
	synchronized void waitForChange() {
		try {
			while(!changed) 
				wait();
			changed = false;
		}catch(InterruptedException e) {
			System.out.println(e);
		}
	}
	synchronized TrafficLightColor getColor(){
		return tlc;
	}
	synchronized void cancel() {
		stop = true;
	}
}
public class TrafficLightDemo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		TrafficLightSimulator t1 = new TrafficLightSimulator(TrafficLightColor.GREEN);
		
		Thread thrd = new Thread(t1);
		thrd.start();
		
		for(int i=0; i<9; i++) {
			System.out.println(t1.getColor());
			t1.waitForChange();
		}
		t1.cancel();
	}

}