Add convenience collect methods to the Stream interface

[forax at univ-mlv.fr]

Hi Rob, Hi Petter, 
we (the lambda EG) have decided against implementing Iterable (see the answer of Brian), so for consistency we have also not enable the right hand side of a enhanced for loop to be a poly-expression (that enables the lambda conversion), hence the mandatory cast.

Rémi

----- Mail original -----
> De: "Peter Levart" <peter.levart at gmail.com>
> À: "Rob Griffin, rgriffin" <Rob.Griffin at quest.com>, "Remi Forax" <forax at univ-mlv.fr>
> Cc: "core-libs-dev" <core-libs-dev at openjdk.java.net>
> Envoyé: Mardi 11 Décembre 2018 14:42:51
> Objet: Re: Add convenience collect methods to the Stream interface

> Hi Rob,
> 
> On 12/10/18 11:11 PM, Rob Griffin (rgriffin) wrote:
>> Hi Remi,
>>
>> There are certainly places where we could do this when we are simply iterating
>> over the results but that is not always the case. However I was disappointed to
>> find that the enhanced for loop can't iterate over a stream so if callers of
>> your example methods where doing something like this
>>
>> for (Employee emp : getAllEmployee()) {
>>    ...
>> }
>>
>> then it would have to change to a forEach call if getAllEmployee returned a
>> Stream.
> 
> You can also get an Iterator from a Stream, so if you need external
> iteration over elements of a Stream you don't have to collect it 1st to
> some Collection:
> 
>     Stream<String> names() {
>         return Stream.of("John", "Jil", "Jack");
>     }
> 
> ...and then...
> 
>         for (String name : (Iterable<String>) names()::iterator) {
>             System.out.println(name);
>         }
> 
> This is hack-ish as it relies on the fact that enhanced for loop calls
> Iterable.iterator() method only once, but is the only way to do it if
> you already have a reference to Stream at hand. This would be more
> correct way of doing it if you can call a factory for Stream:
> 
>         for (String name : (Iterable<String>) () -> names().iterator()) {
>             System.out.println(name);
>         }
> 
> Regards, Peter
> 
> P.S. I wonder why the enhanced for loop doesn't establish a context
> where the type of expression after the colon could be inferred, so no
> cast would be necessary. Perhaps because that type could either be an
> Iterable<T> or a T[] ?