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From "James Carman" <ja...@carmanconsulting.com>
Subject Re: Class I would like to commit to commons Collections
Date Thu, 30 Aug 2007 12:17:22 GMT
What is "Map<C,K,V>" here?  The Map interface only has two type parameters,
right?  Shouldn't it just be Map<K,V>?

On 8/29/07, Stephen Kestle <stephen.kestle@orionhealth.com> wrote:
>
>  Hi John,
>
> I have not opened a ticket yet, but ... I have had very similar
> requirements, and will [most-likely] be putting something in that will solve
> your problem.
>
> However, it will not be a class - consider this method
>
> Map<C, K,V> CollectionUtils.toMap(Collection<C> input, Transformer<C,K>
> keyTransformer, Transformer<C,V> valueTransformer, Map<K,V> map)
>
> You could then do what you wanted, passing in your integer transformer for
> the key, and potentially MultiHashMap for the map.
>
> NB - this is in an ideal (and we're heading to that) collections world.
> MultiHashMap will need to be changed to extend map properly and implement
> the interface in a consistent way (not breaking Map contract etc).
>
> Also note that there will be other variations on the method - most
> commonly
>
> Map<K,V> CollectionUtils.toMap(Collection<V> input, Transformer<V,K>
> keyTransformer){
>      return toMap(input, keyTransformer, NOPTransformer, new
> HashMap<K,V>());
> }
>
> I'll raise a ticket within the next few days - watch this list!
>
> Cheers
>
> Stephen
>
> John wrote:
>
> Hi,
>
> I'm new to the collections mailing list and I have a class I think would
> be appropriate to be donated to the collections API.
>
> This is an extension of the MultiHashMap and filters a given Collection by
> a given field. It will put the objects into the map using the field value as
> the key.
>
> For example, lets say I have a class X which has an integer i. I have four
> instances of X each with the following names and values of i.
>
> x1 i=1
> x2 i=2
> x3 i=2
> x4 i=5
>
> The resulting MultiHashMap will contain the following after a call to
> sortCollection(X.class, "i"); has been made.
>
> key | Objects
> 1   | x1
> 2   | x2, x3
> 5   | x4
>
> I can then get a Collection of sorted objects by asking the map for the
> key value. I find this very useful in many situations I have come across. I
> will of course make the required doc, package and src formatting changes to
> the class before submitting it.
>
> Please can you take a look and tell me if it is worth committing this to
> the Collections repository. What is the process I need to go through before
> committing? I'm a bit pressed for time at the mo' so I can't really spend
> too much time working on the Collections API as a regular developer. I am a
> big fan of the commons Collections API and commons project in general, just
> wish I had more time to get involved.
>
> Kind regards,
>
> John Hunsley.
> Technical Supervisor, Cy-nap Ltd.
>
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> ------------------------------
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>
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