docs: public int nextClearBit(final int i) {
      int x = i >> 6; // i / 64 with sign extension
      long w = ~bitmap.get(x);
      w >>>= i;
      if (w != 0) {
        return i + numberOfTrailingZeros(w);
      }
      int length = bitmap.limit();
      for (++x; x < length; ++x) {
        long map = ~bitmap.get(x);
        if (map != 0L) {
          return x * 64 + numberOfTrailingZeros(map);
        }
      }
      return MAX_CAPACITY;
    }