初体验友元函数

#include <iostream>using namespace std;class Time{public:    Time(int,int,int);//声明构造函数    friend void display(Time &);//声明display函数为Time类的友元函数private:    int hour;    int minute;    int sec;};Time::Time(int h,int m,int s)//定义构造函数，给hour minute sec 赋初值{    hour=h;    minute=m;    sec=s;}void display(Time&t)//这是普通函数，形参t是Time类对象的引用{    cout<<t.hour<<":"<<t.minute<<":"<<t.sec<<endl;}int main(){    Time t1(10,13,56);    display(t1);    return 0;}