HashMap & ConcurrentHashMap Implementation

 

 

 

ConcurrentHashMap

 

ConcurrentHashMap is the Threadsafe.

Default size is 16.

It is Bucket level lock for read /update. N thread can access for read operations.

But  only 16 threads can perform the update or write operation in Concurrent HashMap. 

Each bucket has one lock is Bucket/Segment Lock. Hence It increase the performance.

 

concurrency Level -> Total map divide into n number of blocks.

Concurrency level need not be the same as bucket size.

 

For example: Bucket size is 16 but concurrency level is 8 only. Then each two bucket have one lock.

 

 

ConcurrentHashMap map = new ConcurrentHashMap(int intialcapacity, int loadfactor, int concurrentLevel);

 

Methods

map.put(101,”A”);
map.putIfAbsent(103,”c”);
map.remove(101,”d”);
map.replace(101, “B”, “E”);