实现Runnable接口的线程的子类 [英] subclass of thread implementing Runnable interface

问题描述

让我困惑的是为什么实现runnable接口的线程的子类不会强制我覆盖run方法。基本上，当我创建实现Runnable的简单类时，它会强制我覆盖run方法。但是当我将普通类作为线程的子类时，它并没有强迫我重写该类。这背后的逻辑是什么？

It confuses me why a subclass of thread that implements a runnable interface doesn't force me to override the run method. Basically, when i create simple class that implements Runnable it forces me to override the run method. But when i made the ordinary class a subclass of thread, it didn't force me to override the class anymore. What's the logic behind this?

推荐答案

当一个非抽象类声明它实现了一个接口时，这意味着class必须具有接口定义的每个方法的具体实现，但这些实现方法不必在类中显式，它们可以从超类继承。在这个具体的例子中， java.lang.Thread 有自己的 public void run（），哪个子类继承，所以a实现 Runnable 的Thread的子类不需要添加自己的覆盖来满足编译器（虽然它可能确实有用）。

When a non-abstract class declares that it implements an interface, what that means is that the class must have a concrete implementation of every method that the interface defines, but those implementation methods don't have to be explicit in the class, they could be inherited from a superclass. In this specific example java.lang.Thread has its own public void run(), which subclasses inherit, so a subclass of Thread that implements Runnable doesn't need to add its own override to satisfy the compiler (though it probably does to actually be useful).

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