Atomically incrementing counters stored in ConcurrentHashMap

Question

I would like to collect some metrics from various places in a web app. To keep it simple, all these will be counters and therefore the only modifier operation is to incremen

Answer 1

In Java 8:

ConcurrentHashMap map = new ConcurrentHashMap<>();

map.computeIfAbsent("key", k -> new LongAdder()).increment();