When do you use ConcurrentHashMap

ConcurrentHashMap as an example for fail safe iterator. It allows complete concurrency for retrievals and updates. When there is a scenario where a high number of concurrent updates are expected then ConcurrentHashMap can be used. This is very similar to a Hashtable but does not lock the entire table to provide concurrency and so it is better performance point of view. When there are high number of updates and less number of read concurrently, then ConcurrentHashMap should be used.