code: public double distance(Vector3d v) {
          double dx = x - v.x;
          double dy = y - v.y;
          double dz = z - v.z;
  
          return Math.sqrt(dx * dx + dy * dy + dz * dz);
      }
docs: Returns the Euclidean distance between this vector and vector v.
  
  @return distance between this vector and v