How to stop immediately a task which is started using an ExecutorService?

Question

I have tried many different ways to immediately stop a task which is started using an ExecutorService, with no luck.

Future future = executorServ         


        

Answer 1

What you're doing is very dangerous: you're using a thread pool to execute tasks (which I'll call downloaders), and the same thread pool to execute tasks which

• wait for the downloaders to finish (which I'll call controllers)
• or ask the controllers to stop

This means that if the core number of threads is reached after the controller has started, the downloaders will be put in the queue of the thread pool, and the controller thread will never finish. Similarly, if the core number of threads is reached when you execute the cancelling task, this cancelling task will be put in the queue, and won't execute until some other task is finished.

You should probably use a thread pool for downloaders, another one for controllers, and the current thread to cancel the controllers.