MOOC清华《面向对象程序设计》第3章：流运算符重载实验

#include <iostream>
using namespace std;

class Test{
int id;
public:
Test(int i): id(i) {
cout << "obj_" << id << " created\n";
}
friend istream& operator>> (istream& in, Test& dst);//dst = destination
friend ostream& operator<< (ostream& out, const Test& src);//src = source
};

istream& operator>> (istream& in, Test& dst){
in >> dst.id;
return in;
}

ostream& operator<< (ostream& out, const Test& src){
out << src.id << endl;
return out;
}

int main(){
Test obj(1);  cout << obj;
cin >> obj;   cout << obj;
return 0;
}