public MainWindow() {
        //basic window configuration
        super();
        super.setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
        super.setLocationRelativeTo(null);
        super.setTitle(WINDOW_TITLE);
        super.setResizable(false);
        super.setUndecorated(false);

        //changing L&F
        try {
            UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(MainWindow.class.getName()).log(Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            Logger.getLogger(MainWindow.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            Logger.getLogger(MainWindow.class.getName()).log(Level.SEVERE, null, ex);
        } catch (UnsupportedLookAndFeelException ex) {
            Logger.getLogger(MainWindow.class.getName()).log(Level.SEVERE, null, ex);
        }

        //Programming the closing of the app
        super.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
        super.addWindowListener(new WindowAdapter() {

            @Override
            public void windowClosing(WindowEvent we) {
                sair();
            }

        });

        //setting the icon
        setIconImage(icon);

        //setting the menu
        super.setJMenuBar(createMenuBar());

        super.setVisible(true);
    }