java - run() 方法中的线程状态 (Java)

Question

我想了解 Java 中的多线程。在我介绍 Java 线程可能处于的各种状态时(新的、可运行的、正在运行的、等待/阻塞的、死的)。我尝试运行一些简单的代码来检查线程的状态。

我创建了一个 MyThread 类，它扩展了 Thread 并覆盖了 run() 方法。

package com.practice.threads;

public class MyThread extends Thread {

    @Override
    public void run() {
        super.run();
        System.out.println("Running Mythread.");
        System.out.println("State of thread : " + this.getState()); // line 2
    }

}

现在我已经创建了一个简单的类来测试线程的状态:

package com.practice.threads;

public class ThreadStateDemo {

    /**
     * @param args
     */
    public static void main(String[] args) {
        MyThread myThread = new MyThread();
        System.out.println("State of thread : " + myThread.getState());  // line 1
        myThread.start();

    }

}

运行这个类给出以下输出:

State of thread : NEWRunning Mythread.State of thread : RUNNABLE

第 2 行的输出是我不明白的东西。一个线程实例的run()方法在执行时，怎么会是RUNNABLE状态呢？我在一本书(SCJP Suncertified Programmer)中看到了 RUNNING 状态的提及。它不应该显示 RUNNING 吗？

Answer 1

这本书有一个(容易犯的)错误，状态是RUNNABLE，而不是RUNNING。没有 RUNNING 状态，请参阅 the JavaDoc :

NEW
A thread that has not yet started is in this state.
RUNNABLE
A thread executing in the Java virtual machine is in this state.
BLOCKED
A thread that is blocked waiting for a monitor lock is in this state.
WAITING
A thread that is waiting indefinitely for another thread to perform a particular action is in this state.
TIMED_WAITING
A thread that is waiting for another thread to perform an action for up to a specified waiting time is in this state.
TERMINATED
A thread that has exited is in this state.

(我的重点)

这只是一个奇怪的、有点迂腐的名字，因为从技术上讲，它只有在操作系统运行时才会运行。但从 JVM 的角度来看，它正在“运行”。