Should StreamEx#parallel accept ExecutorService instead of ForkJoinPool?

[JeanFrancoisSavard]

I understand that the default implementation of Stream's use a ForkJoinPool, which I believe is the reason why StreamEx enforce this type.

Am I correct? Else, could the parallel accept a ExecutorService?

[amaembo]

This would not work. Internally parallel stream executes task in current FJP if any or in common pool. It cannot execute in custom ExecutorService, so adding this feature would mean complete reimplementation of stream parallelization which is out of scope of StreamEx.