[9] Review request for 8140503: JavaFX "Pair" Hash Code Collisions

Jim Graham james.graham at oracle.com
Tue Nov 3 19:35:46 UTC 2015

All this does is change the prime constant used to produce the hash value.

Objects.hash(a, b) uses 31*hash(a) + hash(b) instead of the 13*hash(a) + 
hash(b) that the embedded implementation uses.

I don't really think this is a bug.  The fact that Integer objects make 
it easy to reverse engineer and compute collisions of any reasonable 
hash combination computation don't mean that the technique has a bug, it 
just means that the submitter can read the code and think of a 

If there are practical problems being caused for some particular and 
popular use case by the use of this particular constant "13", then we 
need to understand those issues and come up with a more comprehensive 
solution than to simply hand off to another mechanism which uses the 
same procedure with a different prime constant...


On 11/3/15 3:06 AM, Vadim Pakhnushev wrote:
> Hi Chien,
> Could you please review the fix:
> https://bugs.openjdk.java.net/browse/JDK-8140503
> http://cr.openjdk.java.net/~vadim/8140503/webrev.00/
> Thanks,
> Vadim

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