HashMap implementation in Java. How does the bucket index calculation work?
hashmap, java
Solution
It's not calculating the hash, it's calculating the bucket.
The expression `h & (length-1)` does a bit-wise `AND` on `h` using `length-1`, which is like a bit-mask, to return only the low-order bits of `h`, thereby making for a super-fast variant of `h % length`.
Problem
I am looking at the implementation of `HashMap` in Java and am stuck at one point. How is the `indexFor` function calculated? ``` static int indexFor(int h, int length) { return h & (length-1); } ``` Thanks