Java many to many association map

Posted by Raphael Jolivet on Stack Overflow See other posts from Stack Overflow or by Raphael Jolivet
Published on 2010-04-03T15:24:23Z Indexed on 2010/04/03 15:33 UTC
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hashmap

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manytomany

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java

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association

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structure

Hi,

I have to classes, ClassA and ClassB and a "many to many" AssociationClass. I want to use a structure to hold the associations between A and B such as I can know, for each instance of A or B, which are their counterparts.

I thought of using a Hashmap, with pair keys:

Hasmap<Pair<ClassA, ClassB>, AssociationClass> associations;

This way, I can add and remove an association between two instances of ClassA and ClassB, and I can query a relation for two given instances.

However, I miss the feature of getting all associations defined for a given instance of ClassA or ClassB.

I could do it by brute force and loop over all keys of the map to search for associations between a given instance, but this is inefficient and not elegant.

Do you know of any data structure / free library that enables this ? I don't want to reinvent the wheel.

Thanks in advance for your help,

Raphael

NB: This is not a "database" question. These objects are pure POJO used for live computation, I don't need persistence stuff.

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