I want to show the popupmenu when users do the right click on the
menuitem to do something like the mozilla or internet explorer
Favorites menu which can be do right click to show the popup.
I tried this, but i always have the following problems:
1) I open the popupMenu with the popup.show( jmenuitem,
mouseEvent.getX(), mouseEvent.getY())
  I get the error : java.awt.IllegalComponentStateException: component
must be showing on the screen to determine its location

So, I do the menu stay show by overrided the doClick of the jmenuitem
to do nothing. And show the popup with the same way. I got this error.
java.lang.NullPointerException
    at
javax.swing.plaf.basic.BasicPopupMenuUI$MouseGrabber.grabContainer(Unknown
Source)

So, I try to do with the JMenu instead of the JMenuItem....

1.) when i open the popupMenu with
popup.show(jmenu,mouseEvent.getx(),mouseEvent.getY())

the popup is shown, but i can't access an Item in it. When I move the
mouse over the popup then the jmenu will disappears ! And the popup
never disappear!

2.) when i open the popupMenu with
popup.show(someComponent,mouseEvent.getx(),mouseEvent.getY())
the popup is shown, but the oldmenu disappears
in this case the items in the popup are accessible !

Below, this is the fragment of code.
=====================================================
                    //create popupmenu.
    popupMenu = new JPopupMenu();
    popupMenu.add( new JMenuItem("delete this link"));
    popupMenu.add( new JMenuItem("go to this link"));

    //create menubar.
    JMenuBar menuBar = new JMenuBar();

    //create favoritemenu.
    JMenu favoriteMenu = new JMenu("Favorite");
    JMenuItem link1 = new JMenuItem("http://java.sun.com");
    link1.addMouseListener(new MouseAdapter(){
    public void mouseReleased(MouseEvent e) {
           if( SwingUtilities.isRightMouseButton(e) ){ //right-click
         popupMenu.show(e.getComponent(), e.getX(), e.getY());
           } else {
              System.out.println( "left click=" + e.getSource() );
           }
                      }
    });

        favoriteMenu.add( link1 );
       
        menuBar.add( favoriteMenu );

thank's for help