What is hashCode in java how use it?

In Java, every class has a hashCode() method (inherited from Object though it can be overridden) which assigns a 32-bit integer (or hash code) to each instance of that class. This needs to be done in such a way that hash codes are evenly distributed so that clashes (i.e. two instances having the same hash code) are unlikely.

The hashCode() method is then used in the HashTable and other Dictionary-based classes to store and quickly retrieve values based on the hash code of their keys.