Java : je n'arrive pas a charger les images

import java.awt.*;
import java.awt.Image;
import java.awt.event.*;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import javax.swing.JCheckBoxMenuItem;
import javax.swing.JRadioButtonMenuItem;
import javax.swing.ButtonGroup;
import javax.swing.JMenuBar;
import javax.swing.KeyStroke;
import javax.swing.ImageIcon;

import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JTextArea;
import javax.swing.JScrollPane;
import javax.swing.JFrame;
import javax.swing.JButton;

/* MenuLookDemo.java is a 1.4 application that requires images/middle.gif. */

/*
 * This class exists solely to show you what menus look like.
 * It has no menu-related event handling.
 */
class pion{
  Image img;
  
}
public class Chess {
    JTextArea output;
    JScrollPane scrollPane;


    public JMenuBar createMenuBar() {
        JMenuBar menuBar;
        JMenu menu, submenu;
        JMenuItem menuItem;
        JRadioButtonMenuItem rbMenuItem;
        JCheckBoxMenuItem cbMenuItem;

        //Create the menu bar.
        menuBar = new JMenuBar();

        //Build the first menu.
        menu = new JMenu("Game");
        menu.setMnemonic(KeyEvent.VK_A);
        menu.getAccessibleContext().setAccessibleDescription(
                "The only menu in this program that has menu items");
        menuBar.add(menu);
             ImageIcon icon = createImageIcon("images/nba.gif");
        menuItem = new JMenuItem("Nouveau jeu", icon);
        //menuItem.setMnemonic(KeyEvent.VK_T); //used constructor instead
        menuItem.setAccelerator(KeyStroke.getKeyStroke(
                KeyEvent.VK_1, ActionEvent.ALT_MASK));
        menuItem.getAccessibleContext().setAccessibleDescription(
                "Recommencer une partie");
        menu.add(menuItem);

         menu.addSeparator();
        submenu = new JMenu("A submenu");
        submenu.setMnemonic(KeyEvent.VK_S);

        menuItem = new JMenuItem("An item in the submenu");
        menuItem.setAccelerator(KeyStroke.getKeyStroke(
                KeyEvent.VK_2, ActionEvent.ALT_MASK));
        submenu.add(menuItem);

        menuItem = new JMenuItem("Another item");
        submenu.add(menuItem);
        menu.add(submenu);

        //Build second menu in the menu bar.
        menu = new JMenu("Another Menu");
        menu.setMnemonic(KeyEvent.VK_N);
        menu.getAccessibleContext().setAccessibleDescription(
                "This menu does nothing");
        menuBar.add(menu);

        return menuBar;
    } 

    public Container createContentPane() {
        //Create the content-pane-to-be.
       JPanel contentPane = new JPanel(new BorderLayout());
       contentPane.setOpaque(true);
                 JPanel btns[] = new JPanel[64]; 
            JPanel board = new JPanel();
       board.setLayout(new GridLayout(8,8)); 
            int ii = 0; 
        for(int i = 0; i < btns.length; i++) 
        { 
        if(i % 8 == 0)ii++; 
        btns[i] = new JPanel(); 
        btns[i].setBackground(ii % 2 == 1? Color.WHITE:Color.BLACK); 
        btns[i].setPreferredSize(new Dimension(80,80)); 
        board.add(btns[i]); 
        ii++;
        }
      
        contentPane.add(board, BorderLayout.CENTER);

        return contentPane;
    }

    /** Returns an ImageIcon, or null if the path was invalid. */
    protected static ImageIcon createImageIcon(String path) {
        java.net.URL imgURL = Chess.class.getResource(path);
        if (imgURL != null) {
            return new ImageIcon(imgURL);
        } else {
            System.err.println("Couldn't find file: " + path);
            return null;
        }
    }

    private static void createAndShowGUI(){
        //Make sure we have nice window decorations.
        JFrame.setDefaultLookAndFeelDecorated(true);

        //Create and set up the window.
        JFrame frame = new JFrame("Chess STPI v.1.0");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        Chess demo = new Chess();

        frame.setContentPane(demo.createContentPane());
             frame.setJMenuBar(demo.createMenuBar());
        frame.getContentPane();



        //Display the window.
        frame.setSize(800, 600);
        frame.setVisible(true);
    }
    public static void main(String[] args) {
          javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });

    }
}