ConcurrentHashMap vs Synchronized HashMap

Question

What is the difference between using the wrapped class, SynchronizedMap, on a HashMap and ConcurrentHashMap? Is it just being able to modify the hashmap while iterating it (ConcurrentHashMap)?

Answer 1

The short answer:

Both maps are thread-safe implementations of the Map interface. ConcurrentHashMap is implemented for higher throughput in cases where high concurrency is expected.

Brian Goetz's article on the idea behind ConcurrentHashMap is a very good read. Highly recommended.

Answer 2

kindly see the java docs

Answer 3

ConcurrentHashMap is thread safe without synchronizing the whole map. Reads can happen very fast while write is done with a lock.