说明：  设计模式（Design Pattern）是一套被反复使用、多数人知晓的、经过分类的、代码设计经验的总结。使用设计模式的目的：为了代码可重用性、让代码更容易被他人理解、保证代码可靠性。 设计模式使代码编写真正工程化；设计模式是软件工程的基石脉络，如同大厦的结构一样。
(Design patterns are a set of reused, most people know, classified, code design experience summary. The purpose of using design patterns is to reuse code, make it easier for others to understand and ensure code reliability. Design patterns make coding truly engineering; design patterns are the cornerstone of software engineering, just like the structure of a building.)