code: int spread(int x) {
      x = ((x >>> 16) ^ x) * 0x45d9f3b;
      x = ((x >>> 16) ^ x) * 0x45d9f3b;
      return (x >>> 16) ^ x;
    }
docs: Applies a supplemental hash function to a given hashCode, which defends against poor quality
  hash functions.