code: private int cheapRandInt(int max) {
      _seed ^= ( _seed << 21);
      _seed ^= ( _seed >>> 35);
      _seed ^= ( _seed << 4);
      int r = (int) _seed % max;
      return r > 0 ? r : -r;
    }
docs: This is cheap and moderate in quality.
  
  @param max - Upper range limit.
  @return int between 0-(max-1).