java - 同时在java中启动10个不同的线程

Question

我有 10 个不同的线程，我想同时启动它们。同时，我的意思不是按顺序启动它们（尽管这将是关闭的）。

在java中实现这一目标的最佳方法是什么？

Answer 1

To be accurate: You will not be able to start all 10 threads at the exact same time. There will be some difference in the order ms or ns. You can just try to minimize this difference. And even then: If you have less cores than threads the first couple of threads will have done some work before the others even run their first instruction.

Answer 2

这取决于您的计算机拥有的内核数，这些将是同时启动的线程数，这是我在这里的第一个评论，所以我希望这是正确的。

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

public class Practica {

    private static final int NUMTHREADS = 10;

    public static void main(String[] args) {
        CountDownLatch cdl = new CountDownLatch(NUMTHREADS);
        ExecutorService executor = Executors.newFixedThreadPool(NUMTHREADS);
        for (int i = 0; i < NUMTHREADS; i++) {
            executor.submit(new Imp(cdl));
            cdl.countDown();
            System.out.println("one thread sumbmited "+cdl.getCount());
        }
        System.out.println("All threads submmited");
        executor.shutdown();
    }

}

class Imp implements Runnable {
    CountDownLatch cdl;

    public Imp(CountDownLatch arg) {
        this.cdl = arg;
    }

    @Override
    public void run() {
        try {
            cdl.await();
            System.out.printf("STARTED %s at %d millis%n",
                    Thread.currentThread().getName(),
                    System.currentTimeMillis());
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

Answer 3

CountDownLatch在 Javaspecialists 时事通讯The Law of the Corrupt Politician中有一个很好的例子。

public class TestCorruption {
  private static final int THREADS = 2;
  private static final CountDownLatch latch = new CountDownLatch(THREADS);
  private static final BankAccount heinz = new BankAccount(1000);

  public static void main(String[] args) {
    for (int i = 0; i < THREADS; i++) {
      addThread();
    }
    Timer timer = new Timer(true);
    timer.schedule(new TimerTask() {
      public void run() {
        System.out.println(heinz.getBalance());
      }

    }, 100, 1000);
  }

  private static void addThread() {
    new Thread() {
      {
        start();
      }

      public void run() {
        latch.countDown();
        try {
          latch.await();
        } catch (InterruptedException e) {
          return;
        }
        while (true) {
          heinz.deposit(100);
          heinz.withdraw(100);
        }
      }

    };
  }

}