public double dotProduct(final Vector v1, final Vector v2) {
    double _vx = v1.getVx();
    double _dx = v2.getDx();
    double _multiply = (_vx * _dx);
    double _vy = v1.getVy();
    double _dy = v2.getDy();
    double _multiply_1 = (_vy * _dy);
    double _plus = (_multiply + _multiply_1);
    return _plus;
  }