Dispose of JDialog by code, do not let the user close it

I have a short code, I would like to open a dialog, but I do not want the user to be able to close it, it just does not work, help me.

    import javax.swing.*;
    public class Processing extends JOptionPane{

    JDialog jd;
    public Processing(){
        super(null, JOptionPane.DEFAULT_OPTION, 
                  JOptionPane.INFORMATION_MESSAGE, null, new Object[]{});
        Icon processPic = new ImageIcon("C:\\Users\\Judit\\Desktop\\Mesekocka3D"
                + "\\externals\\pics\\szamitas.gif");

        setMessage(processPic);
        jd = createDialog("Számítás");

        jd.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
        jd.setVisible(true);
        jd.dispose();
    }   
}

this is what my code looks like now, I'm using Jdialog instead of Joptionpane, do I have to write more characters for the website to accept my editing?

import javax.swing.*;



public class Mifasz
{
 private static class Processing extends JDialog{

public Processing(){
    Icon processPic = new ImageIcon("C:\\Users\\Judit\\Desktop\\Mesekocka3D"
            + "\\externals\\pics\\szamitas.gif");
    JLabel label = new JLabel(processPic);
    add(label);
    setTitle("Számítás");
    setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);        
    setSize(400, 70);
    setLocation(330, 300);
    setModal(true);
    setVisible(true);
    dispose();
}       
}

  public static void main(String[] args)
  {
    Processing pc = new Processing();
  }

}