8050820: Please add java.util.Optional.stream() to convert Optional<T> to Stream<T>

[Paul Sandoz]

Hi,

http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8050820-Optional-stream/webrev/

This is one of those cases where i think adding a new method to Optional carries enough weight.

It can be really awkward to use Optional with Stream.flatMap to map to a stream of present values. 

It's not at all obvious that one can do "op.map(Stream::of).orElse(Stream.empty()))" so often one sees some contorted code of there in the wild. Hopefully adding Optional.stream (and to the primitive variants) will help reduce such contortions.

A CCC will be filed.  

Thanks,
Paul.