关于重载运算符的再整理

#include<iostream>
using namespace std;
class a
{
public:
    a(int year1,int month1,int day1){year=year1;month=month1;day=day1;}
    friend ostream&operator <<(ostream&output,a&b);
private:
    int year,month,day;
};
ostream&operator <<(ostream&output,a&b)
{
    output<<b.year<<"年"<<b.month<<"月"<<b.day<<"日";
    return output;
}
int main()
{
a b(2022,6,29);
cout<<b;
}

可以结合有参构造函数，直接传递参数进行构造有关函数。