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https://issues.apache.org/jira/browse/COLLECTIONS-213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13038586#comment-13038586
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Matt Benson commented on COLLECTIONS-213:
-----------------------------------------
I would argue that the contract of Iterable suggests implicitly that multiple
.iterator() calls will return multiple Iterator instances. This is not
necessarily about resetting the original instance so much as "forking" it. I
would either make this the default behavior of IteratorIterable, or forego the
public constructor in favor of descriptive factory methods, e.g.:
{{IteratorIterable.adaptForSingleUse(Iterator)}}
{{IteratorIterable.adaptForMultipleUse(Iterator)}}
> CollectionUtils API extension: algorithm methods accept an Iterator argument
> ----------------------------------------------------------------------------
>
> Key: COLLECTIONS-213
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-213
> Project: Commons Collections
> Issue Type: Improvement
> Components: Core
> Reporter: Dusan Chromy
> Assignee: Brent Worden
> Fix For: 4.x
>
> Attachments: COLLECTIONS-213.patch, CollectionUtils.java,
> TestCollectionUtils.java, collections-4.0-213.diff
>
>
> I just finished the Iterator additions to CollectionUtils, including test
> cases and I am going to
> attach them to this issue very shortly (basically as soon as I figure out how
> attaching in JIRA works :)
> At first I was thinking for a while whether CollectionUtils is a good place
> to accomodate the methods with the
> new signature, until I noticed the collect method already accepts an Iterator
> argument.
> Following methods now accept an Iterator argument (besides collect):
> cardinality
> find
> forAllDo
> countMatches
> exists
> I also noticed cardinality used to throw a NPE if the collection argument was
> null.
> I see no reason why it should not return zero. The Iterator flavour does
> return zero
> and I also modified the Collection version to return zero (including Javadoc
> modification) for the sake of consistence.
> I stopped to think for a while before touching the method, but the fact
> that the Javadoc does not mention "may not be null" made me think the NPE is
> not thrown
> intentionally. And after all, cardinality(..) is nothing else than
> specialized countMatches(..),
> which returns 0 for null collection. However, feel free to reject the change
> to the cardinality(Object,Collection)
> method if you think otherwise.
> I worked on a fresh checkout from subversion and I just updated few minutes
> ago to make sure I have modified
> the latest version. Anyway, please double-check before commiting the changes.
> Cheers,
> Dusan
> > I think that these methods would make useful additions to the API.
> >
> > I don't have the time to do much collections work these days, but if you
> > want to code the methods with test cases and attach them to JIRA then that
> > would be great.
> >
> > Stephen
> >
> >
> > dusan.chr...@freenet.de wrote:
> >
> > > I've been using some algorithm methods from the CollectionUtils, for
> > > example
> > > find(Collection, Predicate)
> > > exists(Collection, Predicate)
> > > countMatches(Collection, Predicate)
> > > forAllDo(Collection, Closure)
> > >
> > > However, I would also like to be able to use these algorithms with an
> > > Iterator:
> > >
> > > find(Iterator, Predicate)
> > > exists(Iterator, Predicate)
> > > countMatches(Iterator, Predicate)
> > > forAllDo(Iterator, Closure)
> > >
> > > The obvious workaround is to use IteratorUtils.toList(Iterator), however
> > > this comes at the cost of constructing a list object (an ArrayList
> > > presumably) which could be avoided, as the Iterator itself is sufficient
> > > for the above algorithms to work.
> > >
> > > What do you think? Is there any reason not to provide the algorithms for
> > > an Iterator? I personally think that the algorithms should have been
> > > there for Iterators in the first place, because every collection is
> > > Iterable (or has an Iterator, prior to JDK 5.0).
> > >
> > > If noone is interested or has time to implement these changes, I can also
> > > contribute to the project - but at the moment I just wanted to discuss
> > > the idea / check if this has been already considered or planned.
> > >
> > > Best Regards,
> > >
> > > Dusan Chromy
> >
> >
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