Question

我有10个不同的主题，我想同时开始。同时，我的意思不是按顺序启动它们（尽管这将会很接近）。

在java中实现这一目标的最佳方法是什么？

Answer 1

准确：您将无法在同一时间启动所有10个线程。 ms或ns的顺序会有所不同。你可以尽量减少这种差异。即便如此：如果你的内核少于线程，那么前几个线程在其他线程执行第一条指令之前就会完成一些工作。

Answer 2

在Javaspecialists简报The Law of the Corrupt Politician中有一个使用CountDownLatch的好例子。

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);
        }
      }

    };
  }

}

Answer 3

这取决于您的计算机拥有的核心数量，这将是同时启动的线程数量，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();
        }
    }
}

同时在java中启动10个不同的线程

3 个答案: