Re: [Collections] Equator interface (methods)

[Stephen Kestle <st...@orionhealth.com>]

Stephen Colebourne wrote:
> Stephen Kestle wrote:
>> If an Equator is determined to be something worthwhile for the next 
>> (generic) version of Collections, I can provide interfaces, default 
>> implementations tests etc.
>
> I certainly think that there are multiple ways to to equals checks. In 
> my day job we compare by ==, equals and id.
>
> Done well, this would make a good enhancement in the 'new' collections.
Ok - having got some positive feedback, I will go on to the first issue: 
the Equator interface design.

I propose two methods: one for equality checking, and another for hash 
codes.  This ensures that when used, the general contract of 
Object.equals() and Object.hashCode() are followed in a similar fashion.

There is also the problem of naming here - what should the methods be 
called?  We want it to read well, so we'll start by listing the java 
equals and compare methods.  Summary of the rest of the post: I prefer 
boolean equate() and int hash().

if ( object1.equals(object2) )
    "if object1 equals object2 then..." - pretty simple

if ( object1.compareTo(object2) > 1 )
    "if object1 compare to object2 is greater than 1 then..." - 
"compared to" would make more sense in a sentence, but we favour active 
tenses, since methods are an instruction on an object.  Probably better 
is to phrase it like:
    "if (object1: compare [yourself] to object2) is greater than 1 then..."

if ( comparator.compare(object1, object2) > 1 )
    "if (comparator: compare object1 and object2) is greater than 1 then..."

Getting hash out of the way is easy: hash().  But what's the correct 
verb for equality?

if ( equator.equate(object1, object2) )
    "if (equator: equate object1 and object2) then..." - I prefer this 
one at the moment

if ( equator.equalTo(object1, object2) )
    "if (equator: is object1 equal to object2) then ..." - I have this 
at the moment, but it requires reshuffling of the sentence.

So this post is a bit verbose, but naming is one of the most important 
tasks of development, and since this is rather foundational...

Cheers

Stephen (K)


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