java concurrency: many writers, one reader

Question

I need to gather some statistics in my software and i am trying to make it fast and correct, which is not easy (for me!)

first my code so far with two classes, a StatsS

Answer 1

Chris Dail's answer looks like a good approach.

Another alternative would be to use a concurrent Multiset. There is one in the Google Collections library. You could use this as follows:

private Multiset stats = ConcurrentHashMultiset.create();

public void notify ( String key )
{
    stats.add(key, 1);
}

Looking at the source, this is implemented using a ConcurrentHashMap and using putIfAbsent and the three-argument version of replace to detect concurrent modifications and retry.