RFR: 8272137: Make Iterable classes streamable

[CC007]

On Mon, 9 Aug 2021 12:28:23 GMT, CC007 <github.com+5381337+CC007 at openjdk.org> wrote:

> create Streamable and ParallelStreamable interface and use them in Collection and Optional

The name of this pull request is a bit wrong, but it had to be the same as the JBS name. 

The interfaces don't make the Iterable have stream and parallelStream methods, but are two separate interfaces to denote that an object can be streamed. These interfaces are fully decoupled from the Iterable interface and it is merely suggested that these can be used together in cases that an object is both Iterable and Streamable. No implementation is implied and has to be provided by the object or its superclasses or other interfaces (like collection).

-------------

PR: https://git.openjdk.java.net/jdk/pull/5050