public void actionPerformed(ActionEvent e) {
   mPopupMenu.setVisible(true);
   mPopupMenu.show(mMenuButton, 0, mMenuButton.getHeight());
 }
 public DefaultPopupMenuButtonAction(JPopupMenuButton aMenuButton, JPopupMenu aPopupMenu) {
   mMenuButton = aMenuButton;
   mPopupMenu = aPopupMenu;
   mMenuButton.setPopupMenu(aPopupMenu);
 }