public class Application {

    public static void main(String[] args) {

        SimpleObservable observable = new SimpleObservable();
        SimpleObserver observer1 = new SimpleObserver();
        observer1.setName("Observer 1");
        SimpleObserver observer2 = new SimpleObserver();
        observer2.setName("Observer 2");
        observable.addObserver(observer1);
        observable.addObserver(observer2);

        observable.notifyObservers();


        observable.setState("state 1");
        observable.notifyObservers(new ArrayList<>(Arrays.asList("1","3","3","7")));

        observable.setState("state 2");
        observable.notifyObservers(new ArrayList<>(Arrays.asList("1","4","8","8")));
    }
}


public class SimpleObservable extends Observable {

    private String state;

    public String getState() {
        return state;
    }

    public void setState(String state) {
        setChanged();
        this.state = state;
    }


}
public class SimpleObserver implements Observer {

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public void update(Observable o, Object arg) {

        System.out.println("Observer name: " + this.getName());
        System.out.println("Current state:" + ((SimpleObservable)o).getState()); //так наверное лучше не делать
        System.out.println("Current time:" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").format(new Date()));

        System.out.println(arg);
    }


    @Override
    public String toString() {
        return "SimpleObserver{" +
            "name='" + name + '\'' +
            '}';
    }
}