组合模式
https://bugstack.cn/md/develop/design-pattern/2020-06-08-%E9%87%8D%E5%AD%A6%20Java%20%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F%E3%80%8A%E5%AE%9E%E6%88%98%E7%BB%84%E5%90%88%E6%A8%A1%E5%BC%8F%E3%80%8B.html
组合模式https://bugstack.cn/md/develop/design-pattern/2020-06-08-%E9%87%8D%E5%AD%A6%20Java%20%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F%E3%80%8A%E5%AE%9E%E6%88%98%E7%BB%84%E5%90%88%E6%A8%A1%E5%BC%8F%E3%80%8B.html