Java 8并发-等待任务关闭executor

Question

我正在尝试Java 8并发的第一步。在下面的代码示例中，因为my tasks休眠2秒而引发异常。关机功能等待5秒后终止。因此，只执行两个循环。有没有动态的解决方案，而不是计算执行所需的最大时间并调整awaitTermination()-method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，你还可以使用CountDownLatch，因为你已经知道线程的编号(在本例中是10)。

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();


    }
}

我曾经写过一个比较CountDownLatch，Semaphore和CyclicBarrier的post，它会对你有帮助。