import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.util.ArrayList;

import java.util.List;

import javax.swing.Timer;

public class Data implements Subject, ActionListener {

private List<Observer> observers;

private int state;

private Timer timer;

public Data() {

observers = new ArrayList<Observer>();

timer = new Timer(1000, this);

timer.start();

}

public void attach(Observer o) {

observers.add(o);

}

public void detach(Observer o) {

int index = observers.indexOf(o);

observers.remove(index);

}

public void notifyObservers() {

for(Observer o : observers) {

o.update(state);

}

}

public void actionPerformed(ActionEvent e) {

state = (int) (Math.random() * 10);

notifyObservers();

}

}