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

[Paul Sandoz]

Brian pointed out a incompatibility issue on lambda-dev:

  toArray(null) is now ambiguous and will not compile

This is likely in practice to only affect tests checking the method throws an NPE.

Paul.

On May 30, 2013, at 11:18 AM, Paul Sandoz <Paul.Sandoz at oracle.com> 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.