java - How to implement PriorityBlockingQueue with ThreadPoolExecutor and custom tasks

Question

I've searched a lot but could not find a solutuion to my problem.

I have my own class, BaseTask, that uses a ThreadPoolExecutor to handle tasks. I want task prioritization, but when I try to use a PriorityBlockingQueue I get ClassCastException because the ThreadPoolExecutor wraps my Tasks into a FutureTask object.

This obviously makes sense because the FutureTask does not implement Comparable, but how would I go on to solve the priority problem? I've read that you could override newTaskFor() in ThreadPoolExecutor, but I can not seem to find this method at all...?

Any suggestions would be much appreciated!

Some code to help:

In my BaseTask class I have

private static final BlockingQueue<Runnable> sWorkQueue = new PriorityBlockingQueue<Runnable>();

private static final ThreadFactory sThreadFactory = new ThreadFactory() {
    private final AtomicInteger mCount = new AtomicInteger(1);

    public Thread newThread(Runnable r) {
        return new Thread(r, "AsyncTask #" + mCount.getAndIncrement());
    }
};

private static final BaseThreadPoolExecutor sExecutor = new BaseThreadPoolExecutor(
    1, Integer.MAX_VALUE, 10, TimeUnit.SECONDS, sWorkQueue, sThreadFactory);

private final BaseFutureTask<Result> mFuture;

public BaseTask(int priority) {
    mFuture = new BaseFutureTask<Result>(mWorker, priority);
}

public final BaseTask<Params, Progress, Result> execute(Params... params) {

    /* Some unimportant code here */

    sExecutor.execute(mFuture);
}

In BaseFutureTask class

@Override
public int compareTo(BaseFutureTask another) {
    long diff = this.priority - another.priority;

    return Long.signum(diff);
}

In BaseThreadPoolExecutor class i override the 3 submit methods... The constructor in this class gets called, but none of the submit methods

Answer 1

public class ExecutorPriority {

public static void main(String[] args) {

    PriorityBlockingQueue<Runnable> pq = new PriorityBlockingQueue<Runnable>(20, new ComparePriority());

    Executor exe = new ThreadPoolExecutor(1, 2, 10, TimeUnit.SECONDS, pq);
    exe.execute(new RunWithPriority(2) {

        @Override
        public void run() {

            System.out.println(this.getPriority() + " started");
            try {
                Thread.sleep(3000);
            } catch (InterruptedException ex) {
                Logger.getLogger(ExecutorPriority.class.getName()).log(Level.SEVERE, null, ex);
            }
            System.out.println(this.getPriority() + " finished");
        }
    });
    exe.execute(new RunWithPriority(10) {

        @Override
        public void run() {
            System.out.println(this.getPriority() + " started");
            try {
                Thread.sleep(3000);
            } catch (InterruptedException ex) {
                Logger.getLogger(ExecutorPriority.class.getName()).log(Level.SEVERE, null, ex);
            }
            System.out.println(this.getPriority() + " finished");
        }
    });

}

private static class ComparePriority<T extends RunWithPriority> implements Comparator<T> {

    @Override
    public int compare(T o1, T o2) {
        return o1.getPriority().compareTo(o2.getPriority());
    }
}

}

as you can guess RunWithPriority is an abstract class that is Runnable and has a Integer priority field