RFR: 8319123: Implement JEP 461: Stream Gatherers (Preview) [v8]

[Alan Bateman]

On Tue, 14 Nov 2023 16:35:53 GMT, Viktor Klang <vklang at openjdk.org> wrote:

>> This Pull-Request implements [JEP-461](https://openjdk.org/jeps/461)
>
> Viktor Klang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Unpacking the rethrown exceptions from Gatherers.mapConcurrent()

test/jdk/java/util/stream/GathererAPITest.java line 77:

> 75:             return;
> 76:         }
> 77:         fail("Expected NullPointerException but wasn't thrown!");

If you are updating this test then you could use assertThrows(UnsupportedOperationException.class, supplier::get) here, same in assertThrowsNPE.  It's just a minor thing as I'm reading through some of the tests.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16420#discussion_r1394472880