java - 执行器服务不一致

Question

我正在测试HashIds的碰撞。这里是依赖项:

    <!-- https://mvnrepository.com/artifact/org.hashids/hashids -->
    <dependency>
        <groupId>org.hashids</groupId>
        <artifactId>hashids</artifactId>
        <version>1.0.3</version>
    </dependency>

我正在使用以下代码:

    Hashids hashids = new Hashids("xyz", 6, "0123456789ABCDEFGHJKLMNPQRSTUVWXYZ");

    System.out.println("*******************************************************************");
    System.out.println("Started");

    Set<String> set = new HashSet();

    ExecutorService executor = Executors.newFixedThreadPool(4);

    AtomicLong count = new AtomicLong(0);
    final long max = 10_000_000;
    for (long i = 1; i <= max; i++) {

        executor.execute(() -> {
            set.add(hashids.encode(count.incrementAndGet()));

            // This is just to show me that there is some activity going on
            if (count.get() % 100_000 == 0) {
                System.out.println(count.get() + ": " + new Date());
            }
        });
    }

    // Wait till the executor service tasks are done 
    executor.shutdown();
    while (!executor.isTerminated()) {
        Thread.sleep(1000);
    }

    // Assert that the Set did not receive duplicates
    Assert.assertEquals(max, set.size());

    System.out.println("Ended");
    System.out.println("*******************************************************************");

所以，我放了一个 ExecutorService使其更快一些，但是我遇到了问题。任何一个

ExecutorService未完成，并且卡在那里

Set包含重复值，因此断言失败

使用裸for循环比使用ExecutorService

快得多

这段代码可能有什么问题？

Answer 1

您需要在executor.shutdown() ;之后立即调用executor.awaitTermination

您的Set不是线程安全的，请尝试使用Collections.synchronizedSet(set)包装您的集合，或基于ConcurrentHashMap.newKeySet()创建集合，请参阅有关thread safe set的讨论。