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From Stephen Kestle <stephen.kes...@orionhealth.com>
Subject Re: Class I would like to commit to commons Collections
Date Sun, 02 Sep 2007 21:23:23 GMT
I wouldn't usually reply, in the hopes that you re-read the method 
signature...
C is the input collection
K,V are the usual types for map
There are two transformers Transformer<C,K> and Transformer<C,V> that 
transform the collection input type to the respective map key, value types.

The second signature only has <K,V> as there is no value transformer, so 
the input collection is the type of value.

Cheers

Stephen

James Carman wrote:
> 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 
> <mailto: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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>
>     -- 
>     ------------------------------------------------------------------------
>     * <http://www.orionhealth.com>*
>     	
>     	
>
>     *Stephen Kestle Software Engineer*
>     stephen.kestle@orionhealth.com <mailto:stephen.kestle@orionhealth.com>
>     P: +64 9 638 0619
>     M: +64 27 453 7853
>     F: +64 9 638 0699
>     S: skestle
>     www.orionhealth.com <http://www.orionhealth.com>
>
>
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-- 
------------------------------------------------------------------------
* <http://www.orionhealth.com>*
	
	

*Stephen Kestle Software Engineer*
stephen.kestle@orionhealth.com <mailto:stephen.kestle@orionhealth.com>
P: +64 9 638 0619
M: +64 27 453 7853
F: +64 9 638 0699
S: skestle <callto:skestle>
www.orionhealth.com <http://www.orionhealth.com>


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