Java Swing and Mac view

Question

I'm training with Java and Swing, in Windows the GUI is shown correctly, instead on MAC there are several problems. The JMenuBar is shown in the window, while should be shown in the MAC bar [finder].

Code of JMenuBar:

        JMenuBar menuBar = new JMenuBar();

        preferenceItem.addMouseListener(this);
        printItem.addMouseListener(this);

        menuBar.add(fileMenu);
        fileMenu.add(openItem);
        fileMenu.add(printItem);
        fileMenu.add(exportItem);

        menuBar.add(optionMenu);
        optionMenu.add(preferenceItem);

        setJMenuBar(menuBar);

---

Than another problem is how two panels are shown. As you can see in the previous image backup button, which is in the second panel is shown above the first panel.

public OptionDialog(){
        super();

        setTitle(NOME_APPLICAZIONE);

        Dimension dimensioni = Toolkit.getDefaultToolkit().getScreenSize();
        setLocation((int)(dimensioni.getWidth()/2-getWidth()/2), (int)(dimensioni.getHeight()/2-getHeight()/2));
        this.setVisible(true);
        this.add(pnlDialog, BorderLayout.NORTH);
        this.add(pnlDialogBackup, BorderLayout.SOUTH);


        pnlDialog.setBorder(general);

        GridLayout grid = new GridLayout(7,2,20,5);
        pnlDialog.setLayout(grid);

        pnlDialog.add(lblLingua);
        pnlDialog.add(Language);
        pnlDialog.add(lblCarattere);
        pnlDialog.add(Char);
        pnlDialog.add(lblOrdinamento);
        pnlDialog.add(Order);
        pnlDialog.add(lblScadenza);
        pnlDialog.add(Scadenza);
        pnlDialog.add(lblNotifica);
        pnlDialog.add(Notifica);
        pnlDialog.add(lblTempo);
        pnlDialog.add(Time);
        pnlDialog.add(Applica,BorderLayout.PAGE_END);


        pnlDialogBackup.setBorder(backup);
        pnlDialogBackup.add(Backup);


        Notifica.addItemListener(this);

        lblTempo.setVisible(false);
        Time.setVisible(false);
        setSize(new Dimension(300, 300));
        setResizable(false);
}