第十八日

以点类Point为基类公有派生圆类Circle，并以圆类Circle为基类公有派生球类Sphere，main(void)函数完成对其的测试。

Point类结构说明：

Point类的数据成员包括：
①私有数据成员：X坐标x(double型)，Y坐标y(double型)。
Point类成员函数包括：
①有参构造函数Point(double, double)和拷贝构造函数Point(const  Point  &)，其中有参构造函数参数默认值为0，输出信息“Point Constructor run”，拷贝构造函数输出信息“Point CopyConstructor run”
②析构函数，析构函数输出信息“Point Destructor run”
③公有函数成员：void  setX(double)和double getX() const分别返回和设置X坐标
④公有函数成员：void  setY(double)和double getY() const分别返回和设置Y坐标
⑤公有成员函数void show() const用于显示点的坐标信息，显示格式为：(x,y)
⑥公有成员函数double area() const用于计算点的面积，点的面积为0

class Circle : public Point
{
    protected:
    double radius = 0;
    static double PI;
    public:
    Circle (double a = 0, double b = 0, double c = 0)
    {
        x = a;
        y = b;
        radius = c;
        cout << "Circle Constructor run" << endl;
    }
    Circle (Circle &r) : Point(r)
    {
        x = r.x;
        y = r.y;
        radius = r.radius;
        cout << "Circle CopyConstructor run" << endl;
    }
    ~Circle()
    {
        cout << "Circle Destructor run" << endl;
    }
    void setRadius(double a)
    {
        radius = a;
    }
    double getRadius() const
    {
        return radius;
    }
    double circumference() const
    {
        return PI * 2 * radius;
    }
    double area() const
    {
        return radius * radius * PI;
    }
    void show() const
    {
        cout << "("<< x << ","  << y << "),"<< "Radius="<< radius;
    }
};
double Circle::PI = 3.14159;
class Sphere : public Circle
{
    public:
    Sphere(double a = 0, double b = 0, double c = 0)
    {
        x = a;
        y = b;
        radius = c;
        cout << "Sphere Constructor run" << endl;
    }
    Sphere(Sphere &r) : Circle(r)
    {
        x = r.x;
        y = r.y;
        radius = r.radius;
        cout << "Sphere CopyConstructor run" << endl;
    }
    ~Sphere()
    {
        cout << "Sphere Destructor run" << endl;
    }
    double volume() const
    {
        return 4.0/3*PI*radius*radius*radius;
    }
    double area() const
    {
        return 4.0*PI*radius*radius;
    }
};