public class Client {
  public static void main(String[] args) {
    ConcreteSubject s = new ConcreteSubject();
    s.attatch(new ConcreteObserver(s , "Observer1"));
    s.attatch(new ConcreteObserver(s , "Observer2"));
    s.attatch(new ConcreteObserver(s , "Observer3"));
    s.attatch(new ConcreteObserver(s , "Observer4"));

    s.setSubjectState("NEW");
    s.notifyObservers();
  }
}