如何从线程池中获取线程ID？

Question

我有一个固定的线程池，可以向其提交任务（仅限 5 线程）。我如何找出其中哪个 5 线程执行我的任务（例如“5 的线程 #3 正在执行此任务”）？

ExecutorService taskExecutor = Executors.newFixedThreadPool(5);

//in infinite loop:
taskExecutor.execute(new MyTask());
....

private class MyTask implements Runnable {
    public void run() {
        logger.debug("Thread # XXX is doing this task");//how to get thread id?
    }
}

Answer 1

使用Thread.currentThread()：

private class MyTask implements Runnable {
    public void run() {
        long threadId = Thread.currentThread().getId();
        logger.debug("Thread # " + threadId + " is doing this task");
    }
}

Answer 2

接受的答案回答了有关获取a线程ID的问题，但它不允许您执行“Thread X of Y”消息。线程 ID 在线程之间是唯一的，但不一定从 0 或 1 开始。

这是一个匹配问题的示例：

import java.util.concurrent.*;
class ThreadIdTest {

  public static void main(String[] args) {

    final int numThreads = 5;
    ExecutorService exec = Executors.newFixedThreadPool(numThreads);

    for (int i=0; i<10; i++) {
      exec.execute(new Runnable() {
        public void run() {
          long threadId = Thread.currentThread().getId();
          System.out.println("I am thread " + threadId + " of " + numThreads);
        }
      });
    }

    exec.shutdown();
  }
}

和输出：

burhan@orion:/dev/shm$ javac ThreadIdTest.java && java ThreadIdTest
I am thread 8 of 5
I am thread 9 of 5
I am thread 10 of 5
I am thread 8 of 5
I am thread 9 of 5
I am thread 11 of 5
I am thread 8 of 5
I am thread 9 of 5
I am thread 10 of 5
I am thread 12 of 5

使用模算术进行轻微调整将允许您正确执行“线程 X of Y”：

// modulo gives zero-based results hence the +1
long threadId = Thread.currentThread().getId()%numThreads +1;

新结果:

burhan@orion:/dev/shm$ javac ThreadIdTest.java && java ThreadIdTest  
I am thread 2 of 5 
I am thread 3 of 5 
I am thread 3 of 5 
I am thread 3 of 5 
I am thread 5 of 5 
I am thread 1 of 5 
I am thread 4 of 5 
I am thread 1 of 5 
I am thread 2 of 5 
I am thread 3 of 5 

Answer 3

您可以使用 Thread.getCurrentThread.getId()，但是当 LogRecord 由记录器管理的对象已经具有线程 ID。我认为您在某处缺少记录日志消息的线程 ID 的配置。

Answer 4

如果您正在使用日志记录，那么线程名称将会很有帮助。
线程工厂可以帮助解决这个问题：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;

public class Main {

    static Logger LOG = LoggerFactory.getLogger(Main.class);

    static class MyTask implements Runnable {
        public void run() {
            LOG.info("A pool thread is doing this task");
        }
    }

    public static void main(String[] args) {
        ExecutorService taskExecutor = Executors.newFixedThreadPool(5, new MyThreadFactory());
        taskExecutor.execute(new MyTask());
        taskExecutor.shutdown();
    }
}

class MyThreadFactory implements ThreadFactory {
    private int counter;
    public Thread newThread(Runnable r) {
        return new Thread(r, "My thread # " + counter++);
    }
}

输出：

[   My thread # 0] Main         INFO  A pool thread is doing this task

Answer 5

如果您的类继承自 Thread，您可以使用方法getName和setName来命名每个线程。否则，您只需将 name 字段添加到 MyTask 中，并在构造函数中对其进行初始化。

Answer 6

当前线程的获取方式是：

Thread t = Thread.currentThread();

获得Thread类对象(t)后，就可以使用Thread类的方法来获取所需的信息。

线程 ID 获取：

long tId = t.getId(); // e.g. 14291

线程名称获取：

String tName = t.getName(); // e.g. "pool-29-thread-7"

Answer 7

Thread.currentThread.getId() 的方法 getId 自 19 起已弃用。如果使用，则会发出警告，

@Deprecated(since"19")

Deprecated

This method is not final and may be overriden to return a value that is not the thread ID. Use threadId() instead

建议使用

Thread.currentThread.threadId()