The Liskov Substitution Principle (LSP) is one of the basic principles of object-oriented design. The Richter substitution principle says that wherever a base class can appear, subclasses can certainly appear. LSP is the cornerstone of inheritance reuse. Only when derivative classes can replace base classes and the functions of software units are not affected can base classes be truly reused, and derivative classes can also add new behaviors to base classes. The Richter substitution principle is a supplement to the "open-close" principle. The key step to realize the "open-close" principle is abstraction. The inheritance relationship between the base class and the subclass is the concrete realization of abstraction, so the Richter substitution principle is the specification of the concrete steps to realize abstraction. --From Baidu庞夫人等人都听呆了。陈启摊摊手，说道：正常，都在我的意料之中 寻求着自己失去的愿望，环伊吕波的故事开始了——。歼灭秦军约六百人，也粉碎了秦军分进合击，围而歼的计划。仿佛不指望板栗回答，他自答道：哥哥自己也不知道。
