code: public static Vector addUnmodified(Vector vector1, Vector vector2) {
          if (vector2.length() != vector1.length())
              throw new IllegalArgumentException(
                      "Vectors of different sizes cannot be added");
          return addUnmodified(Vectors.asDouble(vector1),
                               Vectors.asDouble(vector2));
      }
docs: Returns a new {@code Vector} which is the summation of {@code vector2}
  and {@code vector1}.
  
  @param vector1 The first vector to used in a summation.
  @param vector2 The second vector to be used in a summation.
  @return The summation of {code vector1} and {@code vector2}.