RFR: 8005051: default methods for Iterator

[Zhong Yu]

On Fri, Dec 14, 2012 at 4:54 AM, Remi Forax <forax at univ-mlv.fr> wrote:
> Hi Akhil,
>
> On 12/14/2012 02:24 AM, Akhil Arora wrote:
>>
>> As part of the library lambdafication, this patch adds a forEach default
>> method to Iterator, and converts remove() into a default method so that
>> implementations of Iterator no longer have to override remove if they
>> desire the default behavior, which is to throw an
>> UnsupportedOperationException.
>>
>> http://cr.openjdk.java.net/~akhil/8005051.0/webrev/
>>
>> The above patch requires a small patch to an internal class which
>> happens to implement both Iterable and Iterator. Now both Iterable and
>> Iterator supply a default forEach method, so the compiler balks. One
>> minimally intrusive solution is for this class to override both defaults
>> and provide its own version of forEach.
>>
>> http://cr.openjdk.java.net/~akhil/8005053.0/webrev/
>
>
> The issue here is in the code of ASM wich is an external library imported in
> the JDK,
> so not sure it's a good idea to patch it.
>
> Moreover, goggling for "implement Iterable, Iterator" shows that this
> anti-pattern is used too frequently to not step back and see if a better
> solution is not possible.
> https://encrypted.google.com/search?hl=en&q=%22implements+Iterable%3C*%3E%2C+Iterator%3C*%3E%22
>
> We can't remove Collection.forEach without having perf issue because the
> stream pipeline use it.
> Iterator.forEach can be removed but it's a pity because it's really
> convenient,
> a possble solution is to rename Iterator.forEach() to something else.

I agree with renaming the method; it shouldn't be confused with the
typical forEach() on a collection which visits *all* elements; here it
only visits the remaining elements.

>>
>> Please review
>> Thanks
>>
>
> cheers,
> Rémi
>