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From: "Thomas Neidhart (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
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Subject: [jira] [Commented] (COLLECTIONS-530) Rejecting items on predicate
 failure without throwing an Exception
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    [ https://issues.apache.org/jira/browse/COLLECTIONS-530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14015212#comment-14015212 ] 

Thomas Neidhart commented on COLLECTIONS-530:
---------------------------------------------

I like the idea, something like this could be added imo.

We should discuss this first on the mailinglist to get feedback also from other people.

> Rejecting items on predicate failure without throwing an Exception
> ------------------------------------------------------------------
>
>                 Key: COLLECTIONS-530
>                 URL: https://issues.apache.org/jira/browse/COLLECTIONS-530
>             Project: Commons Collections
>          Issue Type: Improvement
>          Components: List
>    Affects Versions: 4.0
>            Reporter: Erik
>
> The PredicatedList class doesn't allow entries that fail the predicate, but throws an Exception on entry.
> The problem I have with this, is that it places the onus of filtering out invalid entries on the caller.
> I typically add items in a loop. The item added is the result of a method call (which returns null if it can't create one).
> This problem is so common for me that I have created my own FilteredList class that simply ignores invalid entries.
> I would like the PredicatedList class to be capable of rejecting items without throwing an exception.
> I don't mind writing the code for this, but there are a great many ways in which this can be done.
> So I was wondering what the interface should look like.
> Separate FilteredList class.
> Works, but seems a little verbose for the purpose
> New factory method: filteredList(List<T> list, Predicate<? super T> predicate) 
> Nice and simple, but doesn't allow extension; other ways of dealing with predicate failure.
> New factory method with enum: predicatedList(List<T> list, Predicate<? super T> predicate, PredicateFailEnum action)
> More verbose to use and adds an extra class, but allows more alternative ways to deal with predicate failure.
> One more nice thing is that it might be less confusing, 
> because choosing between predicatedList and the above filteredList might not be so obvious.
> New factory method with interface: filteredList(List<T> list, Predicate<? super T> predicate, PredicateFailInterface action)
> Complex, but the most flexible way of dealing with predicate failure.



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