Java8 Lambda: concat list

Question

I am trying to execute a stream list and process it.

class A { public List<B> bList; } List<A> aList; aList.stream().map(a -> a.bList).... 

Here I get a few lists.

But I would like to collect all my b in only one list. Any ideas?

Answer 1

What is flatMap for:

 List<B> bList = aList.stream() .flatMap(a -> a.bList.stream()) .collect(Collectors.toList());