enhanced for loop with multiple iteration variables

[Alan Snyder]

Lambdas are clean, but limited in current Java compared to nested blocks.

Are full featured lambdas on the horizon?

If not, then we still need loops and iterators.

  Alan




> On Dec 20, 2018, at 3:00 PM, Remi Forax <forax at univ-mlv.fr> wrote:
> 
> or
>  map.forEach((key, value) -> {
>    ...
>  });
> 
> Rémi
> 
> ----- Mail original -----
>> De: "Brian Goetz" <brian.goetz at oracle.com>
>> À: "Alan Snyder" <fishgarage at cbfiddle.com>, "core-libs-dev" <core-libs-dev at openjdk.java.net>
>> Envoyé: Jeudi 20 Décembre 2018 23:50:15
>> Objet: Re: enhanced for loop with multiple iteration variables
> 
>> For Map, you can do:
>> 
>>     for (Map.Entry<K,V> e : map.entrySet()) { ... }
>> 
>> and you're already there.
>> 
>> 
>> 
>> On 12/19/2018 9:54 AM, Alan Snyder wrote:
>>> Has any consideration been given to supporting iterators that provide more than
>>> one iteration variable in the enhanced for loop?
>>> 
>>> Obvious uses would be maps (keys and values) and lists (indexes and values).
>>> 
>>> I have in mind keeping the syntactic sugar approach by using one or more
>>> extensions of the Iterator/Iterable interfaces, such as, for example:
>>> 
>>> interface Iterator2<E1,E2> extends Iterator<E1> {
>>>   E2 get2();
>>> }
>>> 
>>> with the extra methods providing the values for the extra variables (associated
>>> with the previous call to next).
>>> 
>>> Extending interfaces is not required, but it makes the trailing variables
>>> optional, which might be useful. For example, the same iterator could provide
>>> values or values and keys.
>>> 
>>> The fact that this approach only works for a fixed set of numbers of variables
>>> does not bother me unduly.
>>> 
>>>   Alan
>