docs: public JMenuItem addMenuItem(JMenu menu, String actionKey, char[] rgChars)
      {
          JMenuItem menuItem;
          Action action = (Action)this.get(actionKey);
          if (action == null)
              return null;
          menu.add(menuItem = new JMenuItem(action));
          char firstChar = ActionManager.getFirstChar((String)menuItem.getAction().getValue(Action.NAME), rgChars, false);
          if (firstChar != NO_CHAR)
              menuItem.setMnemonic(firstChar);
          menuItem.setHorizontalTextPosition(JButton.RIGHT);
  
          return menuItem;
      }