code: private static void createAndShowGUI() {
          //Create and set up the window.
          JFrame frame = new JFrame("CardLayoutDemo");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          
          //Create and set up the content pane.
          CardLayoutDemo demo = new CardLayoutDemo();
          demo.addComponentToPane(frame.getContentPane());
          
          //Display the window.
          frame.pack();
          frame.setVisible(true);
      }
docs: Create the GUI and show it.  For thread safety,
  this method should be invoked from the
  event dispatch thread.