C++之文件的输入和输出实例

1.用友元的一个输出 代码如下:

#include <iostream> #include<fstream> using namespace std; class Stu { string name; int age; public: Stu(string n, int a) {name = n; age = a;} friend ostream&operator<<(ostream& out, Stu s) { out << s.name << " " << s.age << endl; return out; } }; int main() { Stu s1("zhang", 20); int a = 3; cout << s1; return 0;}

2.自己新建一个txt文件，然后对它进行输入和输出

代码如下:

#include <iostream> #include<fstream> using namespace std; class Stu { string name; int age; public: Stu(string n = " ", int a = 0) { name = n; age = a; } void show() { cout << name << " " << age << endl; } friend void WriteFile(ofstream& out, Stu& s) { out << s.name << " " << s.age << endl;} friend void ReadFile (ifstream& in , Stu& s) { in >> s.name >> s.age ; } }; int main() { Stu s[3] = { Stu("zhang",20),Stu("lisi",21),Stu("wang",22) }; ofstream out("D:\\S.txt", ios::out);//需要新建一个txt文件并写上文件名 if (!out) { cout << "error"; } for (int i = 0; i < 3; i++) WriteFile(out, s[i]); out.close(); ifstream in("D:\\S.txt", ios::in); Stu st; for (int i = 0; i < 3; i++) { ReadFile(in, s[i]); in.close(); } }