Java Code

[Blicky]

Hello all, I need help with some coding which I have used from a book which I can copy however I need to change something about the program. The idea is that I code a lottery style game where a user clicks a button and 5 random numbers are generated. I have done that, however i can't seem to change the picture on the program. I have done the obvious thing to me which is saving over the "Lotto.png" image thats in the directory in an effort that it will load that picture however it still seems to be displaying the old picture. Here's the files.

package MyJava;

import javax.swing.*;
import java.awt.event.*;

public class Lotto extends JFrame implements ActionListener
{
    // Components.
    ClassLoader ldr = this.getClass().getClassLoader();
    java.net.URL iconURL = ldr.getResource("Lotto.png");
    ImageIcon icon     = new ImageIcon( iconURL );       
    JLabel img      = new JLabel(icon);   
    JTextField txt     = new JTextField( "", 18 );
    JButton btn     = new JButton( "Get My Lucky Numbers" );
    JPanel pnl      = new JPanel();

    // Constructor.
    public Lotto()
    {
        super( "Lotto Application" );
        setSize( 260,200 );
        setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );       
        pnl.add( img );
        pnl.add( txt );
        pnl.add( btn );
        btn.addActionListener( this );
        add( pnl );
        setVisible( true );
    }

    // Event-handler.
    public void actionPerformed( ActionEvent event )
    {
        if( event.getSource() == btn )
        {
            // Declare working variables.
            int[] nums = new int[50];
            String str = "";

            // Fill elements 1-49 with integers 1-49.
            for( int i = 1; i < 50; i++ ) { nums[i] = i; }
        
            // Shuffle the values in elements 1-49.
            for( int i = 1; i < 50; i++ )
            {
                int r = (int) Math.ceil( Math.random() * 49 );
                int temp=nums[i]; nums[i]=nums[r]; nums[r]=temp;
            }

            // Display the values in elements one to six.
            for ( int i = 1; i < 7; i++ )
            {
                str += "  " + Integer.toString(nums[ i ]) + "  ";

            }
            txt.setText( str );
        }
    }

    // Entry point.
    public static void main ( String[] args )
    {
        Lotto lotto = new Lotto();
    }
}

Currently it looks like this

However I want to change that lotto banner image across the top to something else.