public static void main(String[] args) {
	    ConcreteSubject s=new ConcreteSubject();
	    s.attach(new ConcreteObserver(s, "X"));
	    s.attach(new ConcreteObserver(s, "Y"));
	    s.attach(new ConcreteObserver(s, "Z"));
	    
	    s.setSubjectState("ABC");
	    s.unotify();
	}