What are the possible reason for a java.util.concurrent.RejectedExecutionException in a SingleThreadExecutor

Question

I create the following executor in a singleton:

   final private ExecutorService executor = Executors.newSingleThreadExecutor(new ThreadFactory() {
                 


        

Answer 1

You might have submitted tasks after calling executor.shutdown(). Normally to stop executor they do

    executor.shutdown();
    executor.awaitTermination(10, TimeUnit.MINUTES);

Answer 2

Maybe you should use a thread pool instead of using a single executor.

    executor = new java.util.concurrent.ThreadPoolExecutor(30, 30, 60, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(), new ThreadFactory() {
        final AtomicInteger threadNumber = new AtomicInteger( 1 );
        @Override
        public Thread newThread(Runnable r) {
            return new Thread(r, "Thread No : " + threadNumber.getAndIncrement());
        }
    });

Answer 3

There are two reasons why execute would throw a RejectedExecutionException

1. The queue is full and you cannot add any more threads
2. The ThreadPool has been shutdown

Since you are using a LinkedBlockingQueue the only way I can see this occurring is because you shutdown the pool.

Answer 4

Threads are not available to execute the given task. No linked block queue to que task.