设计模式6大原则：
1.单一职责原则(Single Responsibility Principle, SRP)
2.开闭原则(Open-Closed Principle, OCP)
3.里氏代换原则(Liskov Substitution Principle, LSP)
4.依赖倒转原则(Dependency Inversion Principle, DIP)
5.接口隔离原则(Interface Segregation Principle, ISP)
6.迪米特法则(Law of Demeter, LoD)