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.lev...@gmail.com>
> À: "Rob Griffin, rgriffin" <rob.grif...@quest.com>, "Remi Forax"
> <fo...@univ-mlv.fr>
> Cc: "core-libs-dev" <core-libs-dev@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[] ?
