e811. 创建具有嵌套菜单的弹出式菜单

See e810 创建弹出菜单 for an example on how to display a popup menu.

    final JPopupMenu popupMenu = new JPopupMenu();
    
    // Create a submenu with items
    JMenu submenu = new JMenu("SubMenu1");
    submenu.add(action1);
    submenu.add(action2);
    
    // Add submenu to popup menu
    popupMenu.add(submenu);