3 ways to flatten a list of lists. Is there a reason to prefer one of them?

Question

Assume we have a list as follows. CoreResult has a field of type List.

final List list = new LinkedList         


        

Answer 1

Option 3 and 2 is same, so up to you if you want to map first and then flat map or just flatmap.

With option 1 you have to open another stream to perform further operations.