On Thu, Dec 27, 2012 at 1:55 PM, Mike Duigou <mike.dui...@oracle.com> wrote: > I am responding on the StackOverflow thread. I will look into using > ThreadLocalRandom. > > The random.next() is clearly a potential bottleneck but given that this > happens only once per HashMap instance it is still unclear why a reasonable > application would want to create hundreds or thousands of hash maps per > second.
That is pretty common, for example, in a web server, each request may use a HashMap for headers, and there are thousands of requests per second. That's probably not a big deal either on commodity hardware, but OP got 64 cores. Zhong Yu > Mike > > On Dec 27 2012, at 11:38 , Aleksey Shipilev wrote: > >> Looks very like dumb inlined java.util.Random? >> Is there a security threat to use ThreadLocalRandom instead there? >> >> -Aleksey. >> >> On 27.12.2012, at 23:16, Zhong Yu <zhong.j...@gmail.com> wrote: >> >>> Reported by the SO question >>> >>> http://stackoverflow.com/questions/14010906 >>> >>> the HashMap constructor contains a CAS, which is kind of surprising. >>> Could it be removed? >>> >>> transient final int hashSeed = >>> sun.misc.Hashing.randomHashSeed(this); // CAS >>> >>> Zhong Yu >
