RFR: JDK-8205461 Create Collector which merges results of two other collectors

[Peter Levart]

Hi Tagir,

I think this looks very good. It just needs a CSR. Will you file it?

Regards, Peter

On 08/19/2018 11:24 AM, Tagir Valeev wrote:
> Hello, Brian!
>
>> Of the three phases, teeing is the most important and least obvious, so
>> I think something that includes that in the name is going to be
>> helpful.  Perhaps "teeingAndThen" is more evocative and not totally
>> unwieldy.
> Ok, sounds acceptable to me. Renamed pairing to teeingAndThen.
>
>>> By the way looking into CollectorsTest.java I found some minor things to
>>> cleanup:
>>> 1. `.map(mapper::apply)` and `.flatMap(mapper::apply)` can be replaced with
>>> simple `.map(mapper)` and `.flatMap(mapper)` respectively
>> Does IntelliJ have an inspection for eliminating such locutions?
> Sure, that's how I found them. Well, I took the liberty to fix these two things.
>
>>> 2. In many methods redundant `throws ReflectiveOperationException` is
>>> declared while exception is never thrown
>> For test code where a significant fraction of test cases are going to
>> throw something, we often do this, since its easier to just uniformly
>> tag such methods rather than thinking about which test methods actually
>> throw the exception and which don't.  So I think this is harmless
>> (though cleaning it up is harmless too.)
> I'm not thinking about this, because my IDE thinks for me :-) Ok, I'll
> leave them as is for now.
>
>> You may want to optimize the EnumSet mechanics for the case where
>> neither collector has interesting characteristics.
> Added a special case when reported characteristics for either of
> collectors are empty or IDENTITY_FINISH only.
> I think this should be a common case.
>
> The updated webrev is posted here (along with Peter suggestion to
> rename finisher to merger):
> http://cr.openjdk.java.net/~tvaleev/webrev/8205461/r3/
> Also copyright year is updated
>
> With best regards,
> Tagir Valeev