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From "Sebb (JIRA)" <>
Subject [jira] Commented: (LANG-459) Issue in HashCodeBuilder which only shows up under high load multi-threaded usage.
Date Tue, 16 Sep 2008 12:48:44 GMT


Sebb commented on LANG-459:


Yes, my suggested fix is as you mention.

I copied IDKey from Axis, and then replaced 



   new IDKey(value)

throughout. The private toIdentityHashCodeInteger(value) method can then be deleted.

It seems to work for me, but it would be worth trying some more tests.

> Issue in HashCodeBuilder which only shows up under high load multi-threaded usage.
> ----------------------------------------------------------------------------------
>                 Key: LANG-459
>                 URL:
>             Project: Commons Lang
>          Issue Type: Bug
>    Affects Versions: 2.4
>         Environment: All
>            Reporter: Andrew Wilson
>             Fix For: 3.0, Nightly Builds
>         Attachments:,
>   Original Estimate: 0.08h
>  Remaining Estimate: 0.08h
> We found we were having problems with HashCodeBuilder under multi-threaded high load.
> I narrowed this down to the following attached test case.
> When I dug into the code, I found the problem was solved by commenting out the isRegistered
method (though this would break the infinite loop problem).
> ( I did a lot of other digging that I wont bore you with).
> So instead I replaced the HashSet with an ArrayList and just added the object, rather
than the toIdentityHashCodeInteger(object)
> This results in about 5 lines of change.  
> My suspicion is that System.identityHashCode does not return unique values (it is after
all a hashcode method).  The code assumes it will return a unique value and this causes the
problem at high loads.
> The downside is a List vs. a Set, but I believe this is necessary.
> I'd like to submit this fix and have it verified (and perhaps improved).  I am convinced
it is a necessary fix which we have seen show up under high loads.
> Kindest regards, 
> Andrew.

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