为了检查主题,我编写了代码：

public class ThreadPoolTest {
    public static void main(String[] args) throws InterruptedException {
        for (int i = 0; i < 100; i++) {
            if (test() != 5 * 100) {
                throw new RuntimeException("main");
            }
        }
        test();
    }

    private static long test() throws InterruptedException {
        ExecutorService executorService = Executors.newFixedThreadPool(100);
        CountDownLatch countDownLatch = new CountDownLatch(100 * 5);
        Set<Thread> threads = Collections.synchronizedSet(new HashSet<>());
        AtomicLong atomicLong = new AtomicLong();
        for (int i = 0; i < 5 * 100; i++) {
            executorService.submit(new Runnable() {
                @Override
                public void run() {
                    try {
                        threads.add(Thread.currentThread());
                        atomicLong.incrementAndGet();
                        countDownLatch.countDown();
                    } catch (Exception e) {
                        System.out.println(e);
                    }


                }
            });
        }
        executorService.shutdown();
        countDownLatch.await();
        if (threads.size() != 100) {
            throw new RuntimeException("test");
        }
        return atomicLong.get();
    }
}

如您所见,我使用HashSet< Thread>

仅当Thread不可变时,它的用法才是正确的.至少在测试范围内.

据我了解,equals / hashCode没有被覆盖,因此从Object继承.

因此,如果我的测试不正确以及错误在哪里,请回答.
如果您知道更聪明的方法,请分享.

解决方法:

如我的评论中所述,我认为您的代码实际上可以验证test()创建了100个线程并使用它们执行了500个小任务.如果不是这种情况,肯定会触发您的RuntimeException断言.

验证此问题的另一种方法是使用ThreadLocal来计数正在运行的实际线程数.

我创建了以下单元测试,该单元测试使用ThreadLocal来计数执行器创建的线程数.尝试研究其输出,以确信所创建的线程数.

@Test
public void threadCounter() throws Throwable {
    ThreadLocal<Integer> number = new ThreadLocal<Integer>() {
        private final AtomicInteger values = new AtomicInteger();

        @Override
        protected Integer initialValue() {
            return values.getAndIncrement();
        }
    };

    ExecutorService threadPool = Executors.newFixedThreadPool(100);

    for (int i = 0 ; i < 500 ; i++) {
        final int count = i;
        threadPool.submit(() -> System.out.printf("%-4s : %-20s - %s\n", count, Thread.currentThread().getName(), number.get()));
    }

    threadPool.shutdown();
    threadPool.awaitTermination(10, TimeUnit.SECONDS);

    Assert.assertEquals(100, number.get().intValue());

}