cancelButton.setToolTipText("Return to the main menu.");
        cancelButton.setMnemonic(KeyEvent.VK_C);
        btn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String[] options = {"Yes", "No"};
                int choice = JOptionPane.showOptionDialog(null, "Are you sure you "
                        + "want to cancel the operation?\nAll the information will be lost.",
                        "Return to the main menu", JOptionPane.YES_NO_OPTION,
                        JOptionPane.QUESTION_MESSAGE, null, options, options[0]);
                if (choice == YES_OPTION) {
                    dispose();
                    //MainMenuUI mainMenu;
             //       try {
               //         UIManager.setLookAndFeel(
                 //               "javax.swing.plaf.metal.MetalLookAndFeel");
                   //     mainMenu = new MainMenuUI("Main menu:", pl);
                   // } catch (ClassNotFoundException | IllegalAccessException
                     //       | InstantiationException | UnsupportedLookAndFeelException ex) {
                       // JOptionPane.showMessageDialog(null, ex.getMessage(),
                         //       "Error", JOptionPane.ERROR_MESSAGE);
                   // }
                }
            }
        });