code: public static int dotProduct2(
      final int x0,
      final int y0,
      final int x1,
      final int y1)
    {
      final int x = x0 * x1;
      final int y = y0 * y1;
      return x + y;
    }
docs: Calculate the dot product of {@code (x0, y0)} and {@code (x1, y1)}.
  
  @param x0 The X component of the first vector
  @param y0 The Y component of the first vector
  @param x1 The X component of the second vector
  @param y1 The Y component of the second vector
  
  @return The dot product