友元函数练习

#include "stdafx.h"
#include"iostream"
using namespace std;
class Date;

 class Time
 {
 public:
     Time(int h,int m,int s):hour(h),minute(m),sec(s){}
    
  void display(Date & ); //
  
 private:
    int hour,minute,sec;
 };
 
 class Date
 {
 public:
     Date(int y,int m,int d):year(y),month(m),day(d){}
     
     friend void  Time::display(Date &);
    private:
   int year,month,day;
 };
 void Time::display(Date &d )

 {
      
     cout<<d.year<<"/"<<d.month<<"/"<<d.day<<endl;

     cout<<hour<<"."<<minute<<"."<<sec<<endl;
     
 }
int main()

{
    Date d1(2019,3,12),d2(2019,3,11);
    Time t1(12,12,12),t2(11,11,11);
    t1.display(d1) ;
    t2.display(d2);
    system("pause");
    return 0;
}