docs: public int nextSetBit(final int i) {
      int x = i >> 6;
      long w = bitmap[x];
      w >>>= i;
      if (w != 0) {
        return i + numberOfTrailingZeros(w);
      }
      for (++x; x < bitmap.length; ++x) {
        if (bitmap[x] != 0) {
          return x * 64 + numberOfTrailingZeros(bitmap[x]);
        }
      }
      return -1;
    }