1. SRP(Single responsibility principle , 单一职责)
即一个类只做一个事情.
2. OCP(Open-close principle,开闭原则)
Open for extensions, Close for modifications.
3. LSP(Liskvo substitution principle,里氏替换原则)
Inheritance should ensure that any property proved about supertype objects also holds for subtype objects.
当一个子类的实例应该能够替换任何其超类的实例时,它们之间才具有is-A关系.
4. DIP(Dependency Inversion Principle,控制反转原则)
Depend on abstractions , not concrete classes.
Program to interface , not implementations.
5. ISP(Interface isolation principle,接口隔离原则)
不应该强迫客户依赖于它们不用的方法。接口属于客户,不属于它所在的类层次结构。
子网掩码的作用?
http://baike.baidu.com/view/878.htm