- In Concurrent HashMap allows concurrent Read and Thread Safe ‘update’ operation
- To perform Read operation thread will not require any lock but perform update operation thread require a lock, but it is a lock of the particular part(segment/bucket) map instead of total Map.
- Concurrency update achieved by internally dividing by concurrency level (number of locks).
concurrency level(No. of locks) = 16 (default capacity)
- By default, ConcurrentHashMap maintains 16 locks, one for one segment or bucket.
- ConcurrentHashMap allows any number of reading operations but 16 updates operation at a time by default.
- NULL not allow for key and value.
- While the one thread iteration map,the other thread can perform update operation and it will not throw concurrent Modification Exception.
How Performance Increases
- For read operation lock not require
- for update /write operation lock a particular part/segment/bucket but not lock all map
So it get increased performance by concurrent HashMap.