Difference between Hash32 and Hash in Java string Object
java, string
Solution
The performance advantages of `HashMap`s can be "negated" by feeding it carefully chosen keys, so that you get lots of collisions. This reduces the O(1) access/whatever time for a `HashMap` to O(n), significantly reducing performance.
`hash32` is the cached value for an alternative hashing algorithm, used for `String`s, so that if there were too many collisions with the default algorithm a different algorithm could be used to try to reduce the number of collisions. Source here:
Java SE 7u6 introduces an improved, alternative hash function...
The alternative hash function improves the performance of these map implementations when a large number of key hash collisions are encountered.
The alternative hash function is only applied to keys of type String.
`HashMap` was rewritten in Java 8 to use ad-hoc `TreeMap`s for `Comparable` keys if there were too many collisions for any particular bucket, meaning that performance went from O(1) to O(lg n) instead of O(1) to O(n) -- a significant improvement. As `String`s implement `Comparable`, it was decided that the alternative hashing scheme was no longer needed, and it was removed.
Problem
What is the Difference between Hash32 and Hash in String Object While Debugging I have found the String Object displays hash=0 and hash32=0 as shown in below image.Some could please explain the reason it is displayed. Thanks for the Reply