How to ensure garbage collection of a FutureTask that is submitted to a ThreadPoolExecutor and then cancelled?

Question

I am submitting Callable objects to a ThreadPoolExecutor and they seem to be sticking around in memory.

Looking at the heap dump with the M

Answer 1

As a work around could you do something like:

class ClearingCallable implements Callable {
    Callable delegate;
    ClearingCallable(Callable delegate) {
        this.delegate = delegate;
    }

    T call() {
        try {
            return delegate.call();
        } finally {
            delegate = null;
        }
    }
}