//Confirm MsgBox with Yes/No

   String message = "There are commands in the output buffer - really quit?";
   String title = "Really Quit?";
    // display the JOptionPane showConfirmDialog
    int reply = JOptionPane.showConfirmDialog(this, message, title, JOptionPane.YES_NO_OPTION);
    if (reply == JOptionPane.YES_OPTION)
    {
      System.exit(0);
    }