How to wait for all threads to finish, using ExecutorService?

Question

I need to execute some amount of tasks 4 at a time, something like this:

ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
while(...) {
    tas         


        

Answer 1

ExecutorService.invokeAll() does it for you.

ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
List> tasks; // your tasks
// invokeAll() returns when all tasks are complete
List> futures = taskExecutor.invokeAll(tasks);