Scaling problem of HashMap (introduced with alternative hashing)

[Alan Bateman]

On 01/01/2013 23:13, Eric McCorkle wrote:
> Was the original purpose security-oriented?  It seemed to me that the purpose was to make performance pathologies less likely.
>
> Consider, for example, a bad hash function that maps ip addresses directly to their integer representation.  If an application puts entire subnets into a map.  All the addresses will go into contiguous buckets, which increases probability of a collision considerably.  Adding in randomness helps to smooth over these sorts of pathologies.
>
It was related to collisions, particularly where the keys are Strings 
and coming from an untrusted source. There are better solutions for 
handling a huge number of collisions now and we need to change this code 
(ie: get rid of the alternative hashing). For jdk7u then we have to be 
more cautious and I think Mike is going to see about changing it to use 
ThreadLocalRandom.

-Alan.