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From "Stephen Colebourne (JIRA)" <>
Subject [jira] Commented: (COLLECTIONS-242) Add Equator interface for more powerful collections
Date Fri, 09 Mar 2007 23:23:09 GMT


Stephen Colebourne commented on COLLECTIONS-242:

I think such an interface is a useful extension to the collections framework.

> Add Equator interface for more powerful collections
> ---------------------------------------------------
>                 Key: COLLECTIONS-242
>                 URL:
>             Project: Commons Collections
>          Issue Type: Improvement
>          Components: Comparator
>            Reporter: Stephen Kestle
>             Fix For: Generics
> Java has Comparable and Comparator to compare objects, and objects have an equals() method.
But there is no interface  for when an object has multiple ways of being equal.
> e.g.: an database object that has a name, code and a value. Equality could be based on:
> * database id
> * code
> * name and code
> * case-insensitive name
> When extended to collections, this allows us to search for specific
> values (with an EqualsPredicate that takes an Equator), and implement
> Maps and Sets that use specific equators to determine uniqueness.
> I propose that it has two methods:
> boolean equate();
> int hash();
> I shall upload some files when I next get some time.
> NB: This ticket is a summary of the email conversation begun on 5 Jan 2007: "equator
interface" ( 
Stephen C made reference there to creating a FlexiMap, but in my mind, that's additional to
this issue (this interface still needs to be created to be able to stand alone).

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