Improved HashMap performance in Java 8

If you are reading this one which means you are already aware of Java’s the most fast, versatile and most used data structure HashMap. It completely works on a system where the index of the (key, value) stored(or to be stored) will be computed based on two methods hashCode() and equals().

By far everyone knows that it operates at an asymptotic complexity of O(1) with the best hashCode implementation. But there could be collisions occurred by generating the same bucket position for different hashes and could end up forming a LinkedList inside the bucket. In worst case if all the hashes are mapped to the same bucket then all the (key, value) would form a linked list and would result the search operations performed to be O(n).

Here is the answer, HashMap buckets are now binary trees instead of earlier LinkedLists. If the same bucket is mapped to different hashes then the one considered bigger goes to the right and the smaller goes to the left forming a binary tree.

Also HashMap assumes that keys are comparable and so that it can decide an order and insert the elements as along. But if the keys are not Comparable then do not expect a performance improvement rather would be the same way as earlier if there is a heavy hash collision.

Thanks for reading the article !! Hope this helps !!

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