CODEWITHSUNDEEP
javaconcurrency
Homewrecker
Homewrecker

Reputation: 1106

Java 8 concurrency - Wait for tasks to shutdown executor

I am trying my first steps with Java 8 concurrency. In the code example below, an exception is thrown because the my tasks sleep 2 seconds. The shutdown function waits 5 seconds for termination. Therefore, only two loops are executed. Is there a dynamic solution to this instead of counting the max time the execution could take and adjusting the value of the awaitTermination()-method?

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();
        }
    }

Upvotes: 4

Views: 249

Answers (1)

shazin
shazin

Reputation: 21883

Adding to what @AdamSkyWalker mentioned you can use a CountDownLatch as you already know the no of Threads (10 in this case).

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();


    }
}

I wrote a post sometime back on comparing CountDownLatch, Semaphore and CyclicBarrier which will be helpful for you.

Upvotes: 5

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