Active threads in ExecutorService

Question

Any ideas how to determine the number of active threads currently running in an ExecutorService?

Answer 1

Check the sourcecode for Executors.newFixedThreadPool():

return new ThreadPoolExecutor(nThreads, nThreads,
                              0L, TimeUnit.MILLISECONDS,
                              new LinkedBlockingQueue());

ThreadPoolExecutor has a getActiveCount() method. So you might either cast the ExecutorService to ThreadPoolExecutor, or use the above code directly to obtain one. You can then invoke getActiveCount().