c++友元类2

#include <iostream>
#include <cmath>
using namespace std;

class Point
{
private:
double x,y;
friend class Line;
public:
Point(double i=0,double j=0)
{
x=i;
y=j;
}
Point(Point &p) //复制的构造函数
{
x=p.x;
y=p.y;
}
};

class Line //Line是封闭类
{
private:
Point p1,p2;
public:
Line(Point &xp1,Point &xp2):p1(xp1),p2(xp2){} //参数列表赋值法
double GetLength();
};

double Line::GetLength()
{
double dx=p2.x-p1.x;
double dy=p2.y-p1.y;
return sqrt(dx*dx + dy*dy);
}

int main()
{
Point p1,p2(6,8);
Line L1(p1,p2);
cout<<L1.GetLength()<<endl;
return 1;
}