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From "Sergei Ivanov (JIRA)" <>
Subject [jira] Commented: (COLLECTIONS-110) [collections] Support parametized classes with commons.collections.
Date Thu, 01 Jun 2006 21:21:31 GMT
    [ ]

Sergei Ivanov commented on COLLECTIONS-110:

Another problem we are going to face is that some of the current implementation decisions
are not compatible with generics.
First of all, static singleton instances of e.g. various EmptyIterator's and trivial functors
cannot be made generic. They can be wrapped in a static generified getInstance() method, which
would still contain an unchecked cast.
Second, there are many "graceful fallback" cases, which become tricky with generics. Let's
take TransformIterator as an example. Constructing it without a transformer is equivalent
to constructing it with a NOPTransformer. However, NOPTransformer introduces a certain relation
between expected input and output types: output type must be assignable from input type. There
is no such relation (in fact, no relation at all) between generic parameter types for generic
Transformer interface.

> [collections] Support parametized classes with commons.collections.
> -------------------------------------------------------------------
>          Key: COLLECTIONS-110
>          URL:
>      Project: Commons Collections
>         Type: Bug

>  Environment: Operating System: other
> Platform: Other
>     Reporter: Colbert Philippe

> It's time to create a parallel version of commons.collections to support 
> parametized classes of each container class and abstract class.  It's not that 
> hard.  There is a 23 PDF document on Sun Java website describing in detail how 
> it should be done and what to watch out for.
> I already converted a few classes from commons.collection privately for my own 
> needs.  Once you get the hang of it, it's a rather quick process.
> I am even willing to volunteer my time to do some more but I need the 
> collaboration of some of the original programmers to watch over things.

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