为什么Thread类实现为常规类而不是带有run（）方法的
抽象类是抽象的。

Why was the Thread class implemented as a regular class and not an abstract class with run() method being abstract.

这个问题实际上归结为这样一个事实：你应该总是更喜欢构图而不是继承。

This question actually boils down to the fact that you should always prefer composition over inheritance.

如果 Thread 类被声明为 abstract ，则该语言必须提供另一个从程序员可以用来创建 Thread 的类。那么你的问题就是为什么这个扩展$ c>的类来自 Thread 不是 abstract 。如果该语言没有从 Thread 提供 extends 的另一个类，程序员必须创建自己的类。 c $ c>从 Thread 扩展并覆盖 run（）方法。

If the Thread class was declared as abstract, the language would have to provide another class that extended from it which programmers could use to create a Thread. Your question would then be about why this class that extends from Thread is not abstract. If the language did not provide another class that extends from Thread, programmers would have to create their own class that extends from Thread and override the run() method.

如果没有，为什么方法在Thread类中没有被声明为final？

If not, why was the method not declared final in Thread class??

我能给出的唯一可能的解释是，当该类被引入时，该语言的开发人员会看到一些用例来覆盖 start JDK。我使用的第一个Java版本是1.5，我个人没有遇到过用例，我发现需要覆盖 start 。正如JB Nizet在他的回答中所述

The only possible explanation I can give is that the developers of the language saw some use-cases for overriding start when the class was introduced to the JDK. The first version of Java that I used was 1.5 and I personally have not come across a use-case where I found the need to override start. As JB Nizet stated in his answer

如果今天从头开始重新设计Java，那么设计很可能会有所不同

if Java was redesigned from scratch today, there is a good chance the design would be different