Java ExecutorService -Part 2

Shut down ExecutorService

• submit 된 모든 task 들이 완료 될때 까지 대기 후 종료

• submit 된 task 중 남은 것을 리턴하고 강제 종료

• The ExecutorService awaitTermination() method will block the thread calling it until either the ExecutorService has shutdown completely, or until a given time out occurs. The awaitTermination() method is typically called after calling shutdown() or shutdownNow(). Here is an example of calling ExecutorService awaitTermination():

executorService.shutdown();
executorService.awaitTermination(10_000L, TimeUnit.MILLISECONDS );

Cancel task via Future

public class ExecutorServiceExample8 {

    public static void main(String[] args) {

        ExecutorService es = Executors.newFixedThreadPool(1);
        Future<String> future = es.submit(newCallable("Task 1.1"));

        System.out.println(future.isDone());

        boolean mayInterrupt = true;
        future.cancel(mayInterrupt);

        String result = null;
        try {
            result = future.get();
            System.out.println("result = " + result);
        } catch (InterruptedException e) {
        } catch (ExecutionException e) {
        } catch (CancellationException e){
            System.out.println("Cannot call Future.get() since task was cancelled");
        }

				System.out.println(future.isDone());
        es.shutdown();
    }
}

Ideal number of threads in ExecutorService