code: static void checkK(final int k) {
      if ((k < MIN_K) || (k > MAX_K)) {
        throw new SketchesArgumentException(
            "K must be >= " + MIN_K + " and <= " + MAX_K + ": " + k);
      }
    }
docs: Checks the validity of the given value k
  @param k must be greater than 7 and less than 65536.