Swing Worker Threads Not Concurrent

Question

Hi.

It seems that when I instantiate 12 Swing Worker threads, the first six starts to complete its task, it finishes AND then the last six starts and finishes. The behavior I'm looking for is all 12 threads start working at the same time & finish at the same time.

I have the following:

for (int i = 0; i < 12; i++ )
{
        myTask m = new Mytask(i, START);
        m.execute();
}

The myTask m will increment a progress bar from 0 - 100 in increments of 25. I'm getting outlandish behavior that the first six threads start incrementing, they finish at 100, then the last six threads start from 0 and increment, and finish.

Is there a limiting factor on the amount of Swing Worker threads one may have?

Answer 1

Your question says:

The behavior I'm looking for is all 12 threads start working at the same time & finish at the same time.

But you can't guarantee for all Swing workers threads starting concurrently and ending at same time.

Answer 2

SwingWorker class has a static ExecutorService field with MAX_WORKER_THREADS = 10. I'm not certain why you see 6 and not 10. But you cannot go over 10.

    /**
     * number of worker threads.
     */
    private static final int MAX_WORKER_THREADS = 10;

...

    executorService =
                new ThreadPoolExecutor(1, MAX_WORKER_THREADS,
                                       10L, TimeUnit.MINUTES,
                                       new LinkedBlockingQueue<Runnable>(),
                                       threadFactory);

Answer 3

The behavior I'm looking for is all 12 threads start working at the same time & finish at the same time.

A CountDownLatch is designed for this very purpose. Here's a good example using a single SwingWorker and a number of subsidiary threads controlled by the latch.