定义基类shape,它有默认的构造函数和析构函数;
把点point类声明为shape的派生类,它包含两个数据成员x和y 和输出函数display();
把圆circle定义为点point类的派生类,它在点point的基础上增加一个数据成员radius;并增加输出成员函数 display ()和求面积成员函数area()。
#include <iostream>
using namespace std;
class shape
{
public:
shape()
{
cout<<endl<<"constructor"<<endl;
}
~shape()
{
cout<<endl<<"destructor"<<endl;
}
};
class point:public shape
{
private:
double x,y;
public:
point(){
}
point(double a,double b)
{
x=a;
y=b;
}
void display()
{
cout<<"x="<<x<<",y="<<y<<endl;
}
};
class circle:public point
{
private:
double radius;
public:
circle(double c)
> 如果circle和point有必要联系,
> 就写成circle(int c,int a,int b ):point(a,b);
> 如果没有,在point类中要确保point()能工作;
{
radius=c;
}
void display()
{
cout<<"radius="<<radius<<endl;
}
void area()
{
cout<<"area="<<radius*radius*3.14<<endl;
}
};
int main()
{
point p(3,4);
p.display();
circle c(3);
c.display();
c.area();
return 0;
}