设计模式转载一篇博文: https://bugstack.cn/itstack-demo-design/2020/07/02/%E9%87%8D%E5%AD%A6-Java-%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F-%E5%AE%9E%E6%88%98%E7%8A%B6%E6%80%81%E6%A8%A1%E5%BC%8F.html