How do I convert a Java 8 IntStream to a List?

Question

I'm looking at the docs for the IntStream, and I see an toArray method, but no way to go directly to a List<Integer>

Surely there is a way to convert a Stream to a List?

Answer 1

IntStream::boxed

IntStream::boxed turns an IntStream into a Stream<Integer>, which you can then collect into a List:

theIntStream.boxed().collect(Collectors.toList()) 

The boxed method converts the int primitive values of an IntStream into a stream of Integer objects. The word "boxing" names the int ⬌ Integer conversion process. See Oracle Tutorial.

Java 16 and later

Java 16 brought the shorter toList method. Produces an unmodifiable list. Discussed here.

theIntStream.boxed().toList()  

Answer 2

You could also use mapToObj() on a Stream, which takes an IntFunction and returns an object-valued Stream consisting of the results of applying the given function to the elements of this stream.

List<Integer> intList = myIntStream.mapToObj(i->i).collect(Collectors.toList());