了解join（）方法示例 [英] Understanding join() method example

问题描述

Java thread join（）方法让我感到困惑。我有以下示例

The Java thread join() method confuses me a bit. I have following example

class MyThread extends Thread {
    private String name;
    private int sleepTime;
    private Thread waitsFor;

    MyThread(String name, int stime, Thread wa) { … }

    public void run() {
        System.out.print("["+name+" ");

        try { Thread.sleep(sleepTime); }
        catch(InterruptedException ie) { }

        System.out.print(name+"? ");

        if (!(waitsFor == null))
        try { waitsFor.join(); }
        catch(InterruptedException ie) { }

        System.out.print(name+"] ");

和

public class JoinTest2 {
    public static void main (String [] args) {
        Thread t1 = new MyThread("1",1000,null);
        Thread t2 = new MyThread("2",4000,t1);
        Thread t3 = new MyThread("3",600,t2);
        Thread t4 = new MyThread("4",500,t3);
        t1.start();
        t2.start();
        t3.start();
        t4.start();
    }
}

线程终止的顺序是什么？

In which order are the threads terminated?

推荐答案

实际上让您对 Thread.join（）感到困惑？你没有提到具体的任何内容。

What actually confuses you about Thread.join()? You haven't mentioned anything specific.

鉴于 Thread.join（）（如文档说明），等待这个线程要死，然后 t4 将等待 t3 完成，这将等待要 t2 完成，等待 t1 完成。

Given that Thread.join() (as the documentation states), Waits for this thread to die, then t4 will wait for t3 to complete, which will wait for t2 to complete, which will wait for t1 to complete.

因此 t1 将首先完成，然后是 t2 ， t3 和 t4 。

Therefore t1 will complete first, followed by t2, t3, and t4.

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