Custom thread pool in Java 8 parallel stream

Question

Is it possible to specify a custom thread pool for Java 8 parallel stream? I can not find it anywhere.

Imagine that I have a server application and I would like to

Answer 1

If you don't want to rely on implementation hacks, there's always a way to achieve the same by implementing custom collectors that will combine map and collect semantics... and you wouldn't be limited to ForkJoinPool:

list.stream()
  .collect(parallelToList(i -> fetchFromDb(i), executor))
  .join()

Luckily, it's done already here and available on Maven Central: http://github.com/pivovarit/parallel-collectors

Disclaimer: I wrote it and take responsibility for it.