#include<iostream>
using namespace std;

class Point
{
    public:
        Point() : x(0), y(0)
        {
            cout << "Initialize!" << endl;
        }
        Point(int a, int b) : x(a), y(b)
        {
            cout << "Initialize!" << endl;
        }
        friend ostream &operator << (ostream& output, Point& point);
        friend istream &operator > (istream& input, Point &point);
        ~Point()
        {
            cout << "Set free!" << endl;
        }
    private:
        int x, y;
};

ostream &operator << (ostream& output, Point& point)
{
    output << "(" << point.x << "," << point.y << ")" << endl;
    return output;
}
istream &operator>> (istream& input, Point &point)
{
    input >> point.x;
    input >> point.y;
    return input;
}


int main()
{
    Point A(3, 5), B;
    cin >> B;
    cout << A << endl << B << endl;

    return 0;
}

friend istream &operator > (istream& input, Point &point); // >>

好像不对啊 ，不是这样的，我用的是VC++编译的

#include<iostream>
using namespace std;

class Point
{
    public:
        Point() : x(0), y(0)
        {
            cout << "Initialize!" << endl;
        }
        Point(int a, int b) : x(a), y(b)
        {
            cout << "Initialize!" << endl;
        }
        friend ostream &operator << (ostream& output, Point& point)
    {
            output << "(" << point.x << "," << point.y << ")" << endl;
            return output;
    }   
        friend istream &operator >> (istream& input, Point &point)
    {
            input >> point.x;
            input >> point.y;
            return input;
    }
        ~Point()
        {
            cout << "Set free!" << endl;
        }
    private:
        int x, y;
};
int main()
{
    Point A(3, 5), B;
    cin >> B;
    cout << A << endl << B << endl;

    return 0;
} 

这个就是对的，把定义格式放到类体内，，

为什么要这样呢，不是友员函数么，放在外面为什么不行呢？

楼主把#include<iostrema> 改成#include<iostrema>    然后把using namespace std;这一行注释掉就可以通过了

不是吧，有#include<iostrema> 这样的么？
是不是错了
应该是<iostream>的

#include<iostream>
using namespace std;

class Point;
ostream &operator << (ostream& output, Point& point);
istream &operator>> (istream& input, Point &point);

class Point
{
    public:
        Point() : x(0), y(0)
        {
            cout << "Initialize!" << endl;
        }
        Point(int a, int b) : x(a), y(b)
        {
            cout << "Initialize!" << endl;
        }
        friend ostream &operator << (ostream& output, Point& point);
        friend istream &operator >> (istream& input, Point &point);
        ~Point()
        {
            cout << "Set free!" << endl;
        }
    private:
        int x, y;
};

ostream &operator << (ostream& output, Point& point)
{
    output << "(" << point.x << "," << point.y << ")" << endl;
    return output;
}
istream &operator>> (istream& input, Point &point)
{
    input >> point.x;
    input >> point.y;
    return input;
}


int main()
{
    Point A(3, 5), B;
    cin >> B;
    cout << A << endl << B << endl;

    return 0;
} 

错误信息干吗不贴出来