Jar file not showing images

Question

Hi
When I make a runable jar file, my images it not showing if I try it on another computer. I searched the net and most people seems to use URLs instead ImageIO. But that doesnt help me either. Then I get the error message: Uncaught error fetching image:
java.lang.NullPointerException
Code is below. I hope someone can tell me what I should do.
    private Show show;
    private final int unit = 32;    // size of the images
//    private BufferedImage free;
    private Image free;
    private BufferedImage booked;
    private BufferedImage toBeBooked;
    private BufferedImage ableToEdit;
    public TheaterOverview(Show show)
        this.show = show;
//        try
//            free = ImageIO.read(new File("src/images/user_alt2.png"));
//            booked = ImageIO.read(new File("C:/Documents and Settings/Mads/Programmering/Eclipse/workspace/BioBooking/src/images/user_alt.png"));
//            toBeBooked = ImageIO.read(new File("C:/Documents and Settings/Mads/Programmering/Eclipse/workspace/BioBooking/src/images/user.png"));
//            ableToEdit = ImageIO.read(new File("C:/Documents and Settings/Mads/Programmering/Eclipse/workspace/BioBooking/src/images/user-yellow.png"));
//        catch (Exception e)
//            System.out.println("Not able to read images " + e);
        try
            URL myurl = this.getClass().getResource("images/user_alt2.png");
            Toolkit tk = this.getToolkit();
            free = tk.getImage(myurl);
//            free = ImageIO.read(new File("images/user_alt2.png"));
            booked = ImageIO.read(new File("images/images/user_alt.png"));
            toBeBooked = ImageIO.read(new File("images/images/user.png"));
            ableToEdit = ImageIO.read(new File("images/images/user-yellow.png"));
        catch (Exception e)
            System.out.println("Not able to read images " + e);
     * The paint method. Checks what the status is of each seat and draws them accordingly.
    public void paint(Graphics g)
        Show show = getShow();
        int numberOfRows = show.getTheater().getNumberOfRows();
        int numberOfSeatsInRow = show.getTheater().getSeatsPerRow();
        for (int i = 0; i < numberOfRows; i++)
            for (int j =0; j < numberOfSeatsInRow; j++)
                Seat seat = getShow().getRow(i).getSeat(j);
                if(seat.isAbleToEdit())
                    g.drawImage(ableToEdit, j*unit+1, i*unit+1, null);
                else if (seat.isBooked())
                    g.drawImage(booked, j*unit+1, i*unit+1, null);
                else if (!seat.isBooked() && !seat.isSelected())
                    g.drawImage(free, 0, 0, this);
                else if (seat.isSelected())
                    g.drawImage(toBeBooked, j*unit+1, i*unit+1, null);
    }

Answer 1

just work on getting one simple image to .jar OK
e.g. this should .jar OK (after changing image names)
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class Testing
  Image img;
  public void buildGUI()
    try
      java.net.URL url = new java.net.URL(getClass().getResource("Test.gif"), "Test.gif");
      if(url != null) img = javax.imageio.ImageIO.read(url);
    catch(Exception e){}//swallow exception - handled in paintComponent
    JPanel p = new JPanel(){
      public void paintComponent(Graphics g){
        super.paintComponent(g);
        if(img != null) g.drawImage(img,100,100,this);
        else g.drawString("this space for rent",100,100);
    JFrame f = new JFrame();
    f.getContentPane().add(p);
    f.setSize(400,300);
    f.setLocationRelativeTo(null);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
  public static void main(String[] args)
    SwingUtilities.invokeLater(new Runnable(){
      public void run(){
        new Testing().buildGUI();
}put the image in the same folder, make .jar, then try the .jar on another pc
if all OK, change code to locate image file in subfolder, make .jar, then try the .jar on another pc
if all OK now, modify main program accordingly.
note: in .jars, capitalization of the image file names counts
e.g. in my above example, if I change Test.gif to test.gif, the image is not drawn