java之继承 封装 多态

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继承

(1)继承是一种联结类的层次模型,并且允许和鼓励类的重用,它提供了一种明确表述共性的方法。

(2)对象的一个新类可以从现有的类中派生,这个过程称为类继承,新类继承了原始类的特性,新类称为原始类的派生类(子类),而原始类称为新类的基类(父类)。

(3)派生类可以从它的基类那里继承方法和实例变量,并且类可以修改或增加新的方法使之更适合特殊的需要。

封装

(1)封装是把过程和数据包围起来,对数据的访问只能通过已定义的界面。面向对象计算始于这个基本概念,即现实世界可以被描绘成一系列完全自治、封装的对象,这些对象通过一个受保护的接口访问其他对象

多态性

(1)多态性是指允许不同类的对象对同一消息作出响应。

(2)多态性包括参数化多态性和包含多态性。

(3)多态性语言具有灵活、抽象、行为共享、代码共享的优势,很好的解决了应用程序函数同名问题。

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