Question

我使用下面的代码测试多线程，在ThreadDemo的run方法中，我添加了Thread.sleep（milliseconds）方法，但这不会导致输出。删除此方法后，它可以正常工作。有人可以帮助解释这种行为吗？

import java.util.concurrent.*;

public class ThreadTest {
    private static ThreadLocal<Long> counter = new ThreadLocal<>();
public static void main(String[] args) {
    System.out.println("test start");
    counter.set(0l);
    int count = 3;
    ExecutorService executorService = Executors.newFixedThreadPool(count);

    for(int i=0;i<count;i++) {
        String name = "thread-"+i;
        executorService.submit(new ThreadDemo(name,counter));
    }

    System.out.println("test end");

}

public static class ThreadDemo implements Runnable{
    private String name;
    private ThreadLocal<Long> counter;
    public ThreadDemo(String name, ThreadLocal<Long> counter) {
        this.name = name;
        this.counter = counter;
    }

    public void run() {
        while(true) {

        Long val = (counter.get()  == null) ? 1 : ((counter.get()+1)%10);
        counter.set(val);
        System.out.println("name: "+this.name+" val "+val);

        Thread.sleep(10);
        }
    }

}
}

Answer 1

Do not use ThreadLocal with ExecutorService! Is it dangerous to use ThreadLocal with ExecutorService?

If you want store data, use another solution to your problem.

Another problem is you need handle InterruptedException if you use Thread::wait(...), or Thread::sleep(...)

try {
  Thread.sleep(1000);
} catch (InterruptedException e) {
  // TODO Auto-generated catch block
  e.printStackTrace();
}

Another issue is the name of your Thread, check this article: Naming threads and thread-pools of ExecutorService

Use thread names for debug only, your threads in ExecutorService must be stateless.

Answer 2

使用

Thread.currentThread().sleep(1000);// time is in milisecond
System.out.println("Test");// here you may know thread is waiting or not

Thread.sleep方法后，Java线程无法正常工作

2 个答案: