Submenu of a popup menu is displayed partially out of screen with Java 7

The following issue manifests in all releases of Java 7 (incl. 7u4). And not in Java 6.

Reported by NetBeans users on Windows 7 and on Linux.

See original NetBeans bug at:
http://netbeans.org/bugzilla/show_bug.cgi?id=205796

Steps to reproduce on a small sample Java code:
- run the attached NewJFrame class
- position the window close to the bottom of the screen
- right-click into the window to open popup menu
- expand its "submenu"

result: the first few items of the sub-menu are not visible (depending on
screen height). when running with multiple displays, the whole submenu may
appear on secondary screen.

expected: the submenu starts at the top of the screen and all its menu items
are showing.