温馨提示
大家好我是Cbiltps，在我的博客中如果有难以理解的句意，难以用文字表达的重点，我会有配图。所以我的博客配图非常重要！！！
本节的知识点是从我的主体博客中抽出来的，主体博客其实就是起到一个拓展上下文，为所有的知识点体现逻辑顺序的作用。所以，我会把里面有讨论价值的东西单独拉出来，方便大家食用！
欢迎大家指正/补充，加油！
正文开始
抽象类： 一个类被 abstract 修饰，就直接叫抽象类（定义不重要！）
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抽象类不能直接实例化（会直接报错）
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抽象类中可以有普通的方法和成员
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普通类继承了抽象类，这个普通类中必须重写抽象类的所有抽象方法(可以被重写和调用)
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抽象方法不能是
private修饰的 -
一个抽象类B继承了抽象类A，那么这个抽象类A中可以不实现抽象类A的抽象方法！
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在上条继承关系的基础上，普通类C继承了抽象类B，那么A和B中的抽象方法必须被重写！
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抽象类和抽象方法是不能被
final修饰！
Interface: In a class, methods with the same name are considered overloaded if they have different parameter lists ( different parameter types , different numbers of parameters , or even different order of parameters ). At the same time, overloading has no requirement on the return type , which can be the same or different, so the overload cannot be judged by whether the return type is the same .
- Interfaces cannot be instantiated by themselves
- The methods contained in the interface are all
抽象方法, and the fields can only contain静态常量! - Ordinary methods in interfaces cannot have specific implementations . If you want to implement them, you must use the default keyword to modify this method!
- An interface can have a static method , and this static method can have a method body
- The method in the interface must be an abstract method , so abstract can be omitted
- The method in the interface must be public , so the public can be omitted
Note and difference summary:
- Neither can be instantiated individually
- Abstract classes use the extends keyword to inherit abstract classes; subclasses use the keyword implements to implement interfaces
- Abstract methods can have modifiers such as public , protected , and default ; interface methods have the default modifier of public , and other modifiers cannot be used.
- Abstract classes can only be single- inherited ; interfaces can be implemented in multiple ways
- There can be ordinary methods and members in the abstract class ; the methods contained in the interface are all
抽象方法, and the fields can only contain静态常量!
