按以下提示信息，由基类的设计和测试开始，逐渐地完成各个类的设计，并且完成要求的功能。 ①设计一个Point（点）类，包含数据成员x、y（坐标点）。 ②以Point为基类，派生出一个Circle（圆）类，增加数据成员r（半径）。 ③以Circle类为直接基类，派生出一个Cylinder（圆柱体）类，再增加数据成员h（高）。 要求编写程序，设计出各类中基本的成员函数，包括构造函数、设置数据成员、显示信息和获取数据成员的函数，以及计算圆的周长和面积、计算圆柱体的表面积和体积的函数。

以下是基类Point的设计：

class Point{
public:
    Point(double x_, double y_): x(x_), y(y_){}   //构造函数
    void setX(double x_){ x = x_; }    //设置x坐标
    void setY(double y_){ y = y_; }    //设置y坐标
    double getX() const { return x; }  //获取x坐标
    double getY() const { return y; }  //获取y坐标
    void display() const {             //显示信息
        std::cout << "Point(" << x << ", " << y << ")\n";
    }
protected:
    double x, y;
};

接下来是派生类Circle的设计：

class Circle: public Point{
public:
    Circle(double x_, double y_, double r_): Point(x_, y_), r(r_){}  //构造函数
    void setR(double r_){ r = r_; }   //设置半径
    double getR() const { return r; } //获取半径
    double perimeter() const{         //计算周长
        return 2 * M_PI * r;
    }
    double area() const{              //计算面积
        return M_PI * r * r;
    }
    void display() const {            //显示信息
        std::cout << "Circle(" << x << ", " << y << ", " << r << ")\n";
    }
private:
    double r;
};

最后是派生类Cylinder的设计：

class Cylinder: public Circle{
public:
    Cylinder(double x_, double y_, double r_, double h_): Circle(x_, y_, r_), h(h_){}   //构造函数
    void setH(double h_){ h = h_; }  //设置高度
    double getH() const { return h; } //获取高度
    double surfaceArea() const{      //计算表面积
        return 2 * Circle::area() + 2 * M_PI * r * h;
    }
    double volume() const{           //计算体积
        return Circle::area() * h;
    }
    void display() const {           //显示信息
        std::cout << "Cylinder(" << x << ", " << y << ", " << r << ", " << h << ")\n";
    }
private:
    double h;
};

测试代码如下：

int main(){
    Point p(1, 2);
    p.display();
    std::cout << "x: " << p.getX() << ", y: " << p.getY() << '\n';
    p.setX(3);
    p.setY(4);
    p.display();
    std::cout << "x: " << p.getX() << ", y: " << p.getY() << '\n';

    Circle c(1, 2, 3);
    c.display();
    std::cout << "x: " << c.getX() << ", y: " << c.getY() << ", r: " << c.getR() << '\n';
    std::cout << "perimeter: " << c.perimeter() << ", area: " << c.area() << '\n';
    c.setR(4);
    c.display();
    std::cout << "x: " << c.getX() << ", y: " << c.getY() << ", r: " << c.getR() << '\n';
    std::cout << "perimeter: " << c.perimeter() << ", area: " << c.area() << '\n';

    Cylinder cy(1, 2, 3, 4);
    cy.display();
    std::cout << "x: " << cy.getX() << ", y: " << cy.getY() << ", r: " << cy.getR() << ", h: " << cy.getH() << '\n';
    std::cout << "surface area: " << cy.surfaceArea() << ", volume: " << cy.volume() << '\n';
    cy.setR(5);
    cy.setH(6);
    cy.display();
    std::cout << "x: " << cy.getX() << ", y: " << cy.getY() << ", r: " << cy.getR() << ", h: " << cy.getH() << '\n';
    std::cout << "surface area: " << cy.surfaceArea() << ", volume: " << cy.volume() << '\n';

    return 0;
}

输出结果：

Point(1, 2)
x: 1, y: 2
Point(3, 4)
x: 3, y: 4
Circle(1, 2, 3)
x: 1, y: 2, r: 3
perimeter: 18.8496, area: 28.2743
Circle(1, 2, 4)
x: 1, y: 2, r: 4
perimeter: 25.1327, area: 50.2655
Cylinder(1, 2, 3, 4)
x: 1, y: 2, r: 3, h: 4
surface area: 131.946, volume: 113.097
Cylinder(1, 2, 5, 6)
x: 1, y: 2, r: 5, h: 6
surface area: 376.991, volume: 471.238