Change to HashMap hash function in Java 8

Question

In java 8 java.util.Hashmap I noticed a change from:

static int hash(int h) {
    h ^= (h >>> 20) ^ (h >>> 12);
    return h ^ (h >>>          


        

Answer 1

When I ran hash implementation diffences I see time difference in nano seconds as below (not great but can have some effect when the size is huge ~1million+)-

7473 ns – java 7

3981 ns– java 8

If we are talking about well formed keys and hashmap of big size (~million), this might have some impact and this is because of simplified logic.