1.     /* User clicked on the X close-window button
  2.      * This method is the actionListener for the "windowClosing" event for the
  3.      * JFrame.
  4.      * To Create the ActionListener for the JFrame:
  5.      *   Design view > Inspector panel
  6.      *   Right-click on the JFrame, select Properties
  7.      *   1. Set "defaultCloseOperation" to DO_NOTHING
  8.      *   2. Click on Events. Scroll down to the "windowClosing" event.
  9.      *      Click on the down-arrow button to the right of <none>.
  10.      *      Press the Close button.
  11.      *      The actionListener method will be inserted into your code.
  12.      */
  13.     private void formWindowClosing(java.awt.event.WindowEvent evt) {
  14.          shutdownApplication();
  15.     }
  16.  
  17.     /* Called by the actionListeners for File > Exit, and  the
  18.      * red X close-window button.
  19.      */
  20.     private void shutdownApplication() {
  21.  
  22.         // Ask user if they really want to exit
  23.         int choice = JOptionPane.showConfirmDialog(this,
  24.                 "Are you sure you want to exit?", "Confirm Exit",
  25.                 JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);
  26.         // Check user response
  27.         if (choice == JOptionPane.OK_OPTION) {
  28.             System.exit(0);
  29.         }
  30.     }