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From "Thomas Neidhart (JIRA)" <>
Subject [jira] [Updated] (COLLECTIONS-251) improving static factory methods for static importability, conistency
Date Sun, 15 Jul 2012 11:21:34 GMT


Thomas Neidhart updated COLLECTIONS-251:

    Fix Version/s:     (was: 4.0-beta-1)
> improving static factory methods for static importability, conistency
> ---------------------------------------------------------------------
>                 Key: COLLECTIONS-251
>                 URL:
>             Project: Commons Collections
>          Issue Type: Improvement
>          Components: Bag, BidiMap, Buffer, Collection, Comparator, Core, Functor, Iterator,
KeyValue, List, Map, Set
>    Affects Versions: 3.2
>            Reporter: Stephen Kestle
>             Fix For: 4.0
> Commons Collections uses the singleton "getInstance()" pattern and extends it to allow
parameters etc to be passed in.  decorate() serves a similar purpose.
> I propose replacing both of these with getClassName() for the following reasons:
> 1. Static imports would mean that TruePredicate.getInstance() would be replaced with
getTruePredicate().  getInstance() cannot be statically imported, because it is reduced to
one class' getInstance(), where we are likely using many.
> 2. It gives subclasses a way to avoid compiler issues - COLLECTIONS-243 compile problems
are generally because the compiler can't choose between Collection<T> and Set<T>.
 Doing this change completely avoids this issue - even if there is a workaround, this makes
life a lot easier (different compilers - eclipse - will allow things that the Sun one won't).
> 2.1 Overridden and overloaded static methods are a really bad idea
> 2.2 No confusion about what class is being instantiated
> 2.3 As our methods become more useful in the generic sense, the compiler issues increase
until you hit something that just won't work
> 3. Simple migration path - those using TruePredicate.getInstance() can switch to PredicateUtils.truePredicate()
before updating to this version.
> 4. Allows a more consistent user environment.  Following the current pattern means that
most people will have MyTransformer.getInstance(), while using TransformerUtils.nopTransformer().
> Our work will be made a lot easier if we make this change.

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