Java Programming

I'm creating a java thread pool using java 1.5 executor framework.

private ExecutorService executorService = Executors.newFixedThreadPool(threadPoolSize);
public <T> Future<T> submit(Callable<T> task) {
		return executorService.submit(task);
}

Now I want to get the number of working thread at runtime. Is there any java api available to do this using java 1.5 executor framework?

Thanks,
Arpan