executorservice

I have a basic question about how ExecutorService works in Java. It is quite hard to see the difference between simply creating Threads to perform some tasks in parallel and assigning each tasks to the ThreadPool . The ExecutorService also looks very simple and efficient to use, so I was wondering why we don't use it all the time. Is it just a matter of one way executing its job faster than the other ? Here's two very simple examples to show the difference between the two ways : Using executor service: Hello World (task) static class HelloTask implements Runnable { String msg; public HelloTask

I have submitted a task using executors and I need it to stop after some time (e.g. 5 minutes). I have tried doing like this: for (Future<?> fut : e.invokeAll(tasks, 300, TimeUnit.SECONDS)) { try { fut.get(); } catch (CancellationException ex) { fut.cancel(true); tasks.clear(); } catch(ExecutionException ex){ ex.printStackTrace(); //FIXME: gestita con printstack } } But I always get an error: I have a shared Vector that needs to be modified by the tasks and then read by a thread, and even if I stop all the task, if the timeout occurs I get: Exception in thread "Thread-1" java.util

I am trying to code a solution in which a single thread produces I/O-intensive tasks that can be performed in parallel. Each task have significant in-memory data. So I want to be able limit the number of tasks that are pending at a moment. If I create ThreadPoolExecutor like this: ThreadPoolExecutor executor = new ThreadPoolExecutor(numWorkerThreads, numWorkerThreads, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>(maxQueue)); Then the executor.submit(callable) throws RejectedExecutionException when the queue fills up and all the threads are already busy. What can I do to make

ExecutorService pool=Executors.newFixedThreadPool(7); List<Future<Hotel>> future=new ArrayList<Future<Hotel>>(); List<Callable<Hotel>> callList = new ArrayList<Callable<Hotel>>(); for(int i=0;i<=diff;i++){ String str="2013-"+(liDates.get(i).get(Calendar.MONTH)+1)+"-"+liDates.get(i).get(Calendar.DATE); callList.add(new HotelCheapestFare(str)); } future=pool.invokeAll(callList); for(int i=0;i<=future.size();i++){ System.out.println("name is:"+future.get(i).get().getName()); } Now I want pool to invokeAll all the task before getting to the for loop but when I run this program for loop gets

I use an ExecutorService to execute a task. This task can recursively create other tasks which are submitted to the same ExecutorService and those child tasks can do that, too. I now have the problem that I want to wait until all the tasks are done (that is, all tasks are finished and they did not submit new ones) before I continue. I cannot call ExecutorService.shutdown() in the main thread because this prevents new tasks from being accepted by the ExecutorService . And Calling ExecutorService.awaitTermination() seems to do nothing if shutdown hasn't been called. So I am kinda stuck here. It