Adding a vertical separator in PopupMenu, in the task bar

How can I add a vertical separator in the pop up menu of the app in the task bar ?

   tray = SystemTray.getSystemTray();             
   openMenuItem = new MenuItem("Open P");
   stopKLMenuItem = new MenuItem("Stop");
   exitMenuItem = new MenuItem("exit");
   menu.add(exitMenuItem);
   menu.add(stopKLMenuItem);
   menu.addSeparator(); // adds a horizontal separator
   menu.add(openMenuItem);
   trayIcon = new TrayIcon(image,"P",menu);

The statement menu.addSeparator() adds a horizontal separator. I also wanted a vertical separator like :

How do I do this ?

One easy trick is to add an empty icon to the JMenuItem. The look and feel then adds the vertical separator you are looking for (of course, this only works with the Windows L&F, other L&F may render this differently):

And the code that produced it:

import java.awt.AWTException;
import java.awt.SystemTray;
import java.awt.TrayIcon;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;

import javax.swing.ImageIcon;
import javax.swing.JMenuItem;
import javax.swing.JPopupMenu;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestTrayIcon {

    protected void initUI() {

        TrayIcon trayIcon = new TrayIcon(new ImageIcon(
                "http://3.bp.blogspot.com/-nh7fv5FqpU4/TeUbTvAdSkI/AAAAAAAAAUo/Ig53KJGvzlk/s45/avatar.png").getImage());

        final JPopupMenu popupMenu = new JPopupMenu();
        JMenuItem checkBox1 = new JMenuItem("Last checked...", new ImageIcon(new BufferedImage(16, 16, BufferedImage.TYPE_INT_ARGB)));
        JMenuItem checkBox2 = new JMenuItem("Open...");

        popupMenu.add(checkBox1);
        popupMenu.addSeparator();
        popupMenu.add(checkBox2);

        trayIcon.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseReleased(MouseEvent e) {
                if (e.isPopupTrigger()) {
                    popupMenu.setLocation(e.getX(), e.getY());
                    popupMenu.setInvoker(popupMenu);
                    popupMenu.setVisible(true);
                }
            }
        });
        try {
            SystemTray.getSystemTray().add(trayIcon);
        } catch (AWTException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (InstantiationException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IllegalAccessException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (UnsupportedLookAndFeelException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                new TestTrayIcon().initUI();
            }
        });
    }

}