#include <iostream>
using namespace std;
class A
{public:
A(int n,int q,float p):num(n),quantity(q),price(p){}
void total();
static float average();
private:
    int num;
    int quantity;
    int price;
    static float sum;
    static int count;
};
void A::total()
{sum+=price;
count++;}

float A::average()
{return(sum/count);
}

float A::sum=0;
int A::count=0;

int main()
{A a[3]={
    A(101,5,23.5),
    A(102,12,24.56),
    A(103,100,21.5),
};
for(int i=0;i<=3;i++)
a[i].total();
cout<<"total="<<A::sum<<endl;
cout<<"average="<<A::average()<<endl;
return 0;
}

不知道哪里错了 棒棒忙

#include <iostream>
using namespace std;
class A
{public:
A(int n,int q,float p):num(n),quantity(q),price(p){}
void total();
static float average();
private:
    int num;
    int quantity;
    int price;
    static float sum;  //这个成员变量是私有的
    static int count;
};
void A::total()
{sum+=price;
count++;}

float A::average()
{return(sum/count);
}

float A::sum=0;
int A::count=0;

int main()
{A a[3]={
    A(101,5,23.5),
    A(102,12,24.56),
    A(103,100,21.5),
};
for(int i=0;i<=3;i++)
a[i].total();
cout<<"total="<<A::sum<<endl;   //私有成员不能直接访问
cout<<"average="<<A::average()<<endl;
return 0;
}



具体能实现功能我没看

[ 本帖最后由 b06030415 于 2010-6-3 22:44 编辑 ]

sum是类A的私有成员，要得到sum要定义一个对外输出sum的接口，加一个函数，如 static float get_sum(){return sum;}