RFR: JDK-8319123 : Implementation of JEP-461: Stream Gatherers (Preview)

[Viktor Klang]

On Sun, 5 Nov 2023 16:43:33 GMT, Tagir F. Valeev <tvaleev at openjdk.org> wrote:

>> This Pull-Request implements [JEP-461](https://openjdk.org/jeps/461)
>
> src/java.base/share/classes/java/util/stream/GathererOp.java line 162:
> 
>> 160:              * consideration at this point doesn't yield any performance gains.
>> 161:              */
>> 162:             proceed &= integrator.integrate(state, t, this);
> 
> Note that you are exposing the `GatherSink` object to the clients, and it implements a public `Consumer` interface. Clients may use `((Consumer<T>)downstream).accept(something)`, which may produce unpredictable results. Not sure if this is considered to be a problem, but somebody will certainly try to do this!

@amaembo Sorry, I completely missed this comment. I did some research before this and, in fact, this already happens for `mapMulti` (https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/util/stream/ReferencePipeline.java#L450) and blind-casting to implementation details is not advisable.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16420#discussion_r1387106067