p9_9.cpp

相当丰富的C++源码

/************************************
*   p9_9.cpp                        *
*   抽象类的使用                    *
*************************************/
#include<iostream>
using namespace std;
class Shape                      //抽象类
{
public:
   virtual double area()const=0;
   virtual void   show()=0; 
   Shape(){
	   cout<<"shape cons.."<<endl;
   }
};
class Point:public Shape
{
protected:
	int X,Y;
public:
	Point(int X=0,int Y=0)
	{    
       this->X=X,this->Y=Y;  
	}
   	void show()
	{	
      cout<<"("<<X<<","<<Y<<")"<<endl;	
	}
    double area() const  //求面积
	{
		return 0.0; 
    }
};
const double PI=3.14159;
class Circle :public Point
{
protected:
	double radius;   //半径
public:
	Circle( int X, int Y,double R):Point(X,Y)
	{	
		radius=R;   
	}
	double area() const  //求面积
	{
		return PI*radius*radius; 
    }
	void show()
	{
       cout<<"Centre:"<<"("<<X<<","<<Y<<")"<<endl;
       cout<<"radius:"<<radius<<endl;
	}
};
class Cylinder: public Circle
{
private:
	double height;
public:
    Cylinder(int X, int Y, double R, double H):Circle(X,Y,R)
	{  
		height=H;    
	}
	double area()
	{  
       return 2*Circle::area()+2*PI*radius*height;
	}
    void show()
	{
		Circle::show();
	    cout<<"height of cylinder:"<<height<<endl;
	}
};
void main() 
{
    Cylinder CY(100,200,10,50);
	Shape * P;
	P=&CY;
	P->show();
	cout<<"total area:"<<P->area()<<endl;
	Circle Cir(5,10,100);
	Shape &R=Cir;
    R.show();
}