import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;

import javax.swing.BorderFactory;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JPanel;

class ThreadSimple extends Thread {
    int r = 10, debut;
    boolean continuer;
    boolean finir;
    JPanel panneauDisque;
    ThreadSimple(int debut, JPanel panneauDisque) {
	this.debut = debut;
	this.panneauDisque = panneauDisque;
    }
    
  void suspendre() {
      continuer = false;
    }

  synchronized void reprendre() {
	  continuer = true;
	  notify();
    }

  synchronized void stopper() {
	  finir = true;
	  notify();
    }
  
  public void run() {
    Graphics g = panneauDisque.getGraphics();

    continuer = true;
    finir = false;
    for (int i = 0; i < 30; i++) {
	try {
	    sleep(200);   
	    synchronized(this) {	 
		while (!continuer && !finir)wait();
	      }
	  }
	catch (InterruptedException exc) {}
	if (finir) break;
	g.setColor(new Color((debut+528424*i)%Integer.MAX_VALUE));
	g.drawOval(200 - r, 150 - r, 2*r, 2*r);
	r+=2;
      }
  }
}

@SuppressWarnings("serial")
    class PanneauThreadSimple extends JPanel implements ActionListener {
	ThreadSimple thread = null;
	Random alea; 
	JButton tracer = new JButton("tracer");
	JButton pauser = new JButton("pauser");
	JButton stopper = new JButton("stopper");
	JButton effacer = new JButton("effacer");
	JPanel panneauDisque = new JPanel();
	
	PanneauThreadSimple() {
	    setLayout(new BorderLayout(5, 5));
	    JPanel panneauBouton = new JPanel();
	    panneauDisque.setPreferredSize(new Dimension(400,300));
	    tracer.addActionListener(this);
	    pauser.addActionListener(this);
	    stopper.addActionListener(this);
	    effacer.addActionListener(this);
	    panneauBouton.add(tracer);
	    panneauBouton.add(pauser);
	    panneauBouton.add(stopper);
	    panneauBouton.add(effacer);
	    add(panneauBouton, BorderLayout.NORTH);
	    add(panneauDisque, BorderLayout.CENTER);
	    alea = new Random(System.currentTimeMillis());
	    setBorder(BorderFactory.createLineBorder(Color.BLACK));
	}
	
	public void actionPerformed(ActionEvent evt) {
	    Object source = evt.getSource();
	    
	    if (source == tracer)  {
		    int debut= (int)Math.abs(alea.nextLong());
		    
		    if ((thread == null)||(!thread.isAlive())) {
			    thread = new ThreadSimple(debut, this);
			    thread.start();
			}
		    else thread.reprendre();
		}
	    
	    else if ((source == pauser) && (thread != null)) thread.suspendre();
	    
	    else if (source == stopper) {
		    if (thread != null) thread.stopper();
		    thread = null;
		}
	    
	    else if (source == effacer) repaint();
	}
    }

@SuppressWarnings("serial")
    public class EssaiThreadSimpleA extends JApplet { 
	public void init() {
		try {
			SwingUtilities.invokeAndWait(new Runnable() {
				public void run() {
					PanneauThreadSimple ihm = new PanneauThreadSimple();
					ihm.setBorder(BorderFactory.createLineBorder(Color.BLACK));
					setLayout(new FlowLayout(FlowLayout.CENTER));
					add(ihm);
				}
			});
		} 
		catch (Exception e) {
			System.err.println("Impossible de lancer correctement l'applet");
		}	
	} 
}