面向对象程序设计
Object-oriented programming is based on objects to encapsulate data and behavior. It uses two main techniques for assembling and composing functionality into more complex ones, sub-typing and object composition. Object composition is about combining objects within compound objects, and at the same time, ensuring the encapsulation of each object by using their well-defined interface without visibility of their internals. In this regard, object composition differs from data structures, which do not enforce encapsulation.