Why ConcurrentHashMap cannot be locked for exclusive access?

Question

A quote from #JCIP :

\"Since a ConcurrentHashMap cannot be locked for exclusive access, we cannot use client-side locking to create new atomic operatio

Answer 1

The whole point of the ConcurrentHashMap is that read operations never block, i.e. do not have to check for locks. That precludes the ability to have such a lock.

Why we can't just acquire the lock :

You could do that, but you have to do it consistently for all access paths to the map, and then you have completely negated to purpose of a concurrent data structure. It is supposed to be lock-free.