• Hashtable lock all Map, Concurrent HashMap works on bucket level locking.
  • HashTable at a time only one thread can perform the operation, Concurrent HashMap at a time many threads can perform an operation it will lock only required segment/bucket remaining thread work symentously.
  • In case Hashtable waiting time is more so reduce the performance, In case of ConcurrentHashMap waiting is less so increase performance.
  • In the case of Hashtable at a time only one thread can perform on the reading operation, in the case of ConcurrentHashMap, any no of thread can perform any no of the reading operation.
  • In case of HasTable for performing read operation require a lock, In case of Concurrent lock is required for update operation on bucket not to all map