Dynamic Thread Pool

I have a long running process that listens to events and do some intense processing.

Currently I use Executors.newFixedThreadPool(x) to throttle the number of jobs that runs concurrently, but depending of the time of the day, and other various factors, I would like to be able to dynamically increase or decrease the number of concurrent threads.

If I decrease the number of concurrent threads, I want the current running jobs to finish nicely.

Is there a Java library that let me control and dynamically increase or decrease the number of concurrent threads running in a Thread Pool ? (The class must implement ExecutorService).

Do I have to implement it myself ?

via Chebli Mohamed