上传点所谓的定义
Encapsulation is the OO principle most closely associated with hiding a class’s implementation details.
Coupling is the OO principle most closely associated with making sure classes know about
other classes only through their APIs.
Cohesion is the OO principle most closely associated with making sure a class is designed
with a single, well-focused purpose.
Polymorphism is the OO principle most closely associated with allowing a single object to be
seen as having many types.