RFR(s): 8072726: add adapter to convert Enumeration to Iterator (original) (raw)

Stuart Marks stuart.marks at oracle.com
Sun May 17 00:22:24 UTC 2015

Hi guys, really going at it on a Saturday, eh?

On 5/16/15 3:46 PM, Claes Redestad wrote:

I also realized Iterable should typically allow multiple passes over the collection/enumeration, so this wouldn't feel right. Sorry!

So... I'm happy with Stuart's proposal.

Yep, that's the main reason not to have Enumeration extend Iterable. Although it isn't written down explicitly, common usage expects that each call to iterator() produce a fresh instance, positioned at the beginning, independent of other instances.

I would also be happy (happier?) with a stream variant: pc.elements().stream().forEach(this::doSomethingWithPermission);

I think Rémi answered this well.

and remember, prefer composition to inheritance :) ducks :)

Yep. While we're at it, though, the "obvious" alternative is to have Enumeration extend Iterator (as opposed to Iterable). This could work, but it has a fairly big risk of incompatibility. Iterator defines a next() method returning T, and it seems pretty likely that there's code out there that has a next() method. If it returned T, it wouldn't be an error, but the resulting Iterator probably wouldn't function properly. If it returned something other than T, it'd be a big source incompatibility.

Of course, in principle, the same thing could occur with "asIterator". But that seems much less likely to collide with something than "next".

s'marks

/Claes

/Claes Rémi On 2015-05-16 02:37, Stuart Marks wrote: Hi all, Please review this small API enhancement to add a default method "asIterator()" to Enumeration that converts it into an Iterator. Webrev: http://cr.openjdk.java.net/~smarks/reviews/8072726/webrev.0/ Bug: https://bugs.openjdk.java.net/browse/JDK-8072726 Thanks, s'marks

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