Question

I’ve done some search here and couldn’t find an answer, so I think it’s better to ask.
I’m running a little bit expensive algorithm in a simple Java swing application. Let me describe the structure:

In my JPanel run() method:

public void run() {
    while(true) {
        Algorithm alg = new Algorithm(signal);
        new Thread(alg).start();

        //Wait for algorithm to finish 
        signal.await(alg);

        updateInterface();

        Thread.sleep(60L);
    }
}

Algorithm loops through the pixels of a .JPG file, then loops through another large Integer array (length ~ 12000) and returns. There are very no extra expensive calculationslot. I call Thread.sleep(60L) in the Algorithm run() method also.

The udpateInterface() method is very fast, just draw some java.awt.Polygon objects.

Even though I’m calling Thread.sleep(60L), the CPU usage is about 160% on my Mac Book (2.4 GHz Intel Core 2 Duo, Mem 4GB 1067).

Is there a way I can run this without melting my computer? I’m using CountDownLatch as
a wait notify mechanism.

Thanks!

Answer 1

I would use the following pattern to schedule a repeating task.

private ScheduledExecutorService executorService = null;

public void start() {
    if (executorService != null && !executorService.isShutdown()) return;

    executorService = Executors.newSingleThreadScheduledExecutor();
        executorService.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                Algorithm alg = new Algorithm(signal);
                alg.run();
                updateInterface();
            }
        }, 0, 60, TimeUnit.MILLISECONDS);
}

public void stop() {
    if (executorService != null)
        executorService.shutdown();
}