下面程序的运行结果为（ ）。
#include <iostream>
using namespace std;
class Box
{public:
Box(int w=10,int h=10,int len=10);
int volume();
private:
int height;
int width;
int length;
};
Box::Box(int w,int h,int len)
{height=h;
width=w;
length=len;
}
int Box::volume()
{return(height*width*length);
}
int main()
{
Box box1;
cout<<"The volume of box1 is "<<box1.volume()<<endl;
Box box2(15);
cout<<"The volume of box2 is "<<box2.volume()<<endl;
Box box3(15,30);
cout<<"The volume of box3 is "<<box3.volume()<<endl;
Box box4(15,30,20);
cout<<"The volume of box4 is "<<box4.volume()<<endl;
return 0;
}
出自：南阳师范学院-计算机网络技术