Loose ends: Collection.toArray(IntFunction<A[]> generator)

[Remi Forax]

On 05/30/2013 11:18 AM, Paul Sandoz wrote:
> A while ago there was some lively discussion on toArray and we finally settled on the following method in Stream:
>
>        <A> A[] toArray(IntFunction<A[]> generator);
>
> Due to "noise" of other stuff i think we forgot to discuss whether it is valuable to add a similar default method to Collection (as recently suggested by Peter Levart on the lambda-dev list which motivated this email).
>
>
> The functionality can already be achieved with:
>
>    c.stream().toArray(String[]::new);
>
> but is not likely to be as efficient as the existing concrete Collection.toArray implementations (e.g. see ArrayList.toArray)
>
> This is also the way to produce an array in parallel:
>
>    c.parallelStream().toArray(String[]::new);
>
> where efficiencies can be obtained if the collection is large enough.
>
>
> But we could also add to Collection:
>
>      default <T> T[] toArray(IntFunction<T[]> generator) {
>          return toArray(generator.apply(size()));
>      }
>
>      c.toArray(String[]::new);
>
> Seems like a reasonable thing to do. The sequentially efficiency is retained without the "stink" of using the other toArray method accepting an array instance (of or not of the right length).
>
> Paul.

good idea,
current toArray(T[]) is awkward to use and has a weird semantics.

Rémi