Programmation Java/swing/Boutons sur image

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import javax.swing.*;
import java.io.*;
import java.net.*;
 
public class FormulaireImage {
 
   public static void main(String[] args) {
                JFrame f = new JFrame("Formulaire");
                JLayeredPane l = new JLayeredPane(); 
                l.setPreferredSize(new Dimension(150,150));
                JPanel pi = new JPanel() {
                        public void paint(Graphics g) {
                                try {
                                        URL ImageWB = new URL("http://upload.wikimedia.org/wikipedia/commons/6/64/Wikibooks-logo-fr.png");
                                        BufferedImage image1 = ImageIO.read(ImageWB);
                                        g.drawImage(image1, 0, 0, null);
                                } catch (IOException e) {
                                        e.printStackTrace();
                                }
                        }
                };
                pi.setBounds(10,10,150,150);    // Fenêtre 150*150 placée à aux coordonnées 10,10 
                l.add(pi,new Integer(0));       // Déposée sur la couche zéro
 
                JPanel pb = new JPanel();
                JButton b1 = new JButton("Bouton 1");
                b1.addActionListener(new ActionListener(){
                        public void actionPerformed(ActionEvent e) {
                                System.out.println("Clic bouton 1");
                        }
                });
                pb.add(b1);
                JButton b2 = new JButton("Bouton 2");
                b2.addActionListener(new ActionListener(){
                        public void actionPerformed(ActionEvent e) {
                                System.out.println("Clic bouton 2");
                        }
                });             
                pb.add(b2);
                pb.setBounds(30,30,100,60);
                l.add(pb,new Integer(1));
                f.add(l);
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.pack();
                f.setVisible(true);     // Ou show(); deprecated
   }
}