Java 8 并发 - 等待任务关闭执行器

Question

我正在尝试 Java 8 并发性的第一步。 在下面的代码示例中，抛出异常是因为我的任务 hibernate 了 2 秒。关机功能等待 5 秒以终止。因此，只执行了两个循环。是否有动态解决方案而不是计算执行可能花费的最长时间并调整 awaitTermination() 方法的值？

public class Application {

    public static void main(String[] args) {
        ExecutorService executor = Executors.newFixedThreadPool(1);

        IntStream.range(0, 10).forEach(i ->
                executor.submit(() -> {
                    try {
                        TimeUnit.SECONDS.sleep(2);
                        System.out.println("Hello");
                    } catch (InterruptedException e) {
                        throw new IllegalStateException("Task interrupted", e);
                    }
                })
        );

        shutdown(executor);
    }

    private static void shutdown(ExecutorService executor) {
        try {
            executor.shutdown();
            executor.awaitTermination(5, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            System.err.println("tasks interrupted");
        } finally {
            if (!executor.isTerminated()) {
                System.err.println("cancel non-finished tasks");
            }
            executor.shutdownNow();
        }
    }

Answer 1

除了@AdamSkyWalker 提到的内容之外，您还可以使用 CountDownLatch，因为您已经知道线程数(在本例中为 10 个)。

public static void main(String[] args) throws Exception {
        ExecutorService executor = Executors.newFixedThreadPool(1);
        final CountDownLatch latch = new CountDownLatch(10);

        IntStream.range(0, 10).forEach(i ->
                executor.submit(() -> {
                    try {
                        TimeUnit.SECONDS.sleep(2);
                        System.out.println("Hello");
                    } catch (InterruptedException e) {
                        throw new IllegalStateException("Task interrupted", e);
                    } finally {
                        latch.countDown();
                    }
                })
        );

        latch.await();


    }
}

我写了一个post有时回过头来比较 CountDownLatch、Semaphore 和 CyclicBarrier，这会对您有所帮助。