What is a ConcurrentHashMap?

The enhancement of HashMap in Java is known as ConcurrentHashMap. Both of the Java classes have lots of similarities but ConcurrentHashMap works more effectively during runtime when you are trying to modify. One can also say that it is an alternative to HashMap in Java 1.5. It provides more safety and security in a multithreaded environment along with better performance. Unlike HashMap it doesn't lock the whole map instead it goes with a portion of the map. You can operate multiple threads without any complication on a single object. The Default level of concurrency in it is 16 and as per the concurrency level, there is a division of object into segments.