C++继承

Circular圆形类

/*圆形类*/
class Circular
{
private:
	const static double PI;
	double R = 0;
public:
	Circular() = default;
	Circular(double r);
	double GetArea();    /*圆面积*/
	double GetGirth();   /*圆周长*/
};
const double Circular::PI = 3.14;

Circular::Circular(double r): R {r} {}
/*圆面积*/
double Circular::GetArea()
{
	double S = PI * R * R;
	return S;
}
/*圆周长*/
double Circular::GetGirth()
{
	double L = 2 * PI * R;
	return L;
}

Cylinder圆柱体类

/*圆柱体类*/
class Cylinder: public Circular
{
private: 
	double H = 0;
public:
	Cylinder() = default;
	Cylinder(double r,double h);
	double GetVolume();        /*圆柱体体积*/
	double GetSurfaceArea();   /*圆柱体表面积*/

};

Cylinder::Cylinder(double r, double h) : Circular{ r }, H{ h } {}
/*圆柱体体积*/
double Cylinder::GetVolume()
{
	double V = H * GetArea();
	return V;
}
/*圆柱体表面积*/
double Cylinder::GetSurfaceArea()
{
	double S = 2 * GetArea() + H * GetGirth();
	return S;
}

测试：

#include "Circular.h"

#include <iostream>
using namespace std;

int main(void)
{
	Circular Cir{ 10 };
	cout << "圆面积：" << Cir.GetArea() << endl;
	cout << "圆周长：" << Cir.GetGirth() << endl;
	Cylinder Cy{ 5,10 };
	cout << "底面积：" << Cy.GetArea() << endl;
	cout << "体积：" << Cy.GetVolume() << endl;
	cout << "底周长：" << Cy.GetGirth() << endl;
	cout << "表面积：" << Cy.GetSurfaceArea() << endl;
	return 0;
}

测试结果：