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From Felix Knecht <fel...@apache.org>
Subject Re: Equals and HashCode
Date Mon, 17 May 2010 13:33:44 GMT
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On 05/17/10 15:30, Emmanuel Lecharny wrote:
> On 5/17/10 1:44 PM, Felix Knecht wrote:
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>>
>>   
>>> IMO, writing a decent HashCode() method is simple. No need to use this
>>> HashCodeBuilder that don't lnow how to deal with Object (it simply add
>>> the object.hashcode() to the computed hash code, which is bad).
>>>      
>> I don't see whats bad doing so. The rule is "if two objects are equal,
>> then their hashCode values must be equal as well". As a very bad
>> solution we can just return 1111 in every case :(
>>    
> It's bad as it carries the semantic, not the logic. In other words, ypu
> may have two objects considered as different when they are equals, just
> because you were too lazzy to implement the hashcode method. I give you
> an example : comparing two Entry instance in the server is just about
> comparing their DN, nothing else. If you call the HashcodeBuilder on it,
> you will get errors if the Attributes are the same, but stored in a
> different order, which is not expected.

I see. Thanks for explanation.

> 
> Of course, this is a case by case issue.
> 
> What I mean here is that hashcode computation must be contextual.
> 

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