numberOfActors is a ConcurrentHashMap<Option<String>, AtomicLong>, so it will return an AtomicLong -- that's also the reason why the casting isn't applied at declaration site, to make it obvious what it 'really' is, since it's declared as an _uncast_ long.

The value is 'numberOfActors' for 'className', but 'numberOfActorsForClassName' seemed a bit redundant, given the names of the map and key object.