title: JPopupMenu and Jmenu problem
body: <p>I have a <code>JPopupMenu</code> lets call it (aaa) inside it i have <code>Jmenu(mmm)</code> ,contain some <code>JmenuItems(like b,c,d,k)</code>.
  this popup menu shows at right click on the panel ,and on mouse over mmm menu the sub <code>menu (b,c,d,k)</code> appear ,but if i goes down a little bit under the mmm menu ,the sub <code>menu (b,c,d,k)</code> disappear ,how i can solve this to be more friendly ?can i make the sub <code>menu (b,c,d,k)</code> appear with left mouse click over the mmm menu?</p>
  
  <pre><code>JPopupMenu aaa = new JPopupMenu();
  JMenu mmm = new JMenu("mmm");
  JMenuItem b = new JMenuItem("b");
  JMenuItem c = new JMenuItem("c");
  JMenuItem d = new JMenuItem("d");
  JMenuItem k = new JMenuItem("k");
  mmm.add(b);
  mmm.add(c);
  mmm.add(d);
  mmm.add(k);
  aaa.add(mmm);
  </code></pre>