[10?] RFR: 8193128: Reduce number of implementation classes returned by List/Set/Map.of() (original) (raw)

Claes Redestad claes.redestad at oracle.com
Sat Dec 9 16:04:04 UTC 2017

Hi Andrej,

forEach seems like a no-brainer, but spliterator might require some extra care.

For example, returning Spliterators.emptySpliterator() and Collections.singletonSpliterator when appropriate sounds like nice little optimizations, but Arrays.spliterator(T[]) with an empty or single-element array appears to be relatively cheap operations, whereas mixing implementation could make call-sites accepting List.of(foo).spliterator() become megamorphic.

Thus I think these should be done independently as a follow-up, along with tests and microbenchmarks.

Thanks!

/Claes

On 2017-12-09 11:43, Andrej Golovnin wrote:

Hi Claes,

One more thing: Could you please add specialised implementations also for the following methods:

List.forEach(Consumer) List.spliterator() For List12 when List12.size() == 1 please use Collections.singletonSpliterator() (this method should be moved to the Spliterators class and be public). For List12 when List12.size() == 2 please use Arrays.spliterator(). For ListN when List.isEmpty() == true please use Spliterators.emptySpliterator​() and otherwise use Arrays.spliterator(). I’m sorry I forgot to mention, that Set12, SetN, Map12 and MapN should also have specialised implementations for the #forEach-methods and for the #spliterator()-methods in Set12, SetN. Thanks! Best regards, Andrej Golovnin

More information about the core-libs-dev mailing list