code: public RadialMenuItem addMenuItem (String command, String label, Image icon, Predicate predicate)
      {
          RadialMenuItem item = new RadialMenuItem(command, label, new ImageIcon(icon), predicate);
          addMenuItem(item);
          return item;
      }
docs: Adds a menu item to the menu. The menu should not currently be active.
  
  @param command the command to be issued when the item is selected.
  @param label the textual label to be displayed with the menu item.
  @param icon the icon to display next to the menu text or null if no
  icon is desired.
  @param predicate a predicate that will be used to determine whether or not this menu item
  should be included in the menu and enabled when it is shown.
  
  @return the item that was added to the menu. It can be modified while the menu is not being
  displayed.