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“Java子类与继承（五）”

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Java Subclasses and Inheritance (5)，

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一、abstract类和abstract方法

用关键字abstract修饰的类为抽象类；用abstract修饰的方法就是抽象方法。

The classes modified by the keyword abstract are abstract classes. Methods modified with abstract are abstract methods.

在抽象类中，既可以有抽象方法，又可以有非抽象方法；在普通类中者不含抽象方法，否则就报错。

In an abstract class, there can be both abstract methods and non-abstract methods. Does not contain abstract methods in ordinary classes, otherwise an error is reported.

抽象类是框架，对象无法开辟空间。抽象类一般作为父类，子类继承父类变量和方法，继承的抽象方法需要重写。因此，抽象方法不能被final修饰。

Abstract class framework, cannot be used to create objects. Abstract classes generally act as parent classes, and subclasses inherit parent variables and methods. Inherited abstract methods need to be overwritten. Therefore, abstract methods cannot be modified by final.

抽象类的子类可以是抽象的，也可以是非抽象的。如果是非抽象的，子类必须重写父类的抽象方法；如果子类是抽象的，子类可以重写，也可以继承。

A subclass of an abstract class can be abstract or non-abstract. If it is non-abstract, the subclass must override the abstract method of the parent class; If the subclass is abstract, the subclass can be overridden or inherited.

抽象类声明对象不能开辟空间，但是非抽象的子类可以，可以利用上转型对象完成。该上转型对象在调用方法时有些不同。调用的是子类重写的方法而不是子类隐藏或继承的方法。

Abstract classes declare that objects cannot open up space, but non-abstract subclasses can, and can do so using up-transition objects. The up-transition object calls methods somewhat differently. It calls methods that the subclass overrides, not methods that the subclass hides or inherits.

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参考资料

翻译：网易有道翻译

参考文献：Java2实用教程

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