使用默认参数的构造函数

#include <iostream>
using namespace std;
class Box
{
public:
    Box(int h=10,int w=10,int len=10);
    int volume();
private:
    int height;
    int width;
    int length;
};
Box::Box(int h,int w,int len)
{
    height=h;
    width=w;
    length=len;
}
int Box::volume()
{
    return (height*width*length);
}
int main()
{
    Box box1;
    cout<<"The vlume of box1 is "<<box1.volume()<<endl;
    Box box2(15);
    cout<<"The vlume of box2 is "<<box2.volume()<<endl;
    Box box3(15,30);
    cout<<"The vlume of box3 is "<<box3.volume()<<endl;
    Box box4(15,30,20);
    cout<<"The vlume of box4 is "<<box4.volume()<<endl;
    return 0;
}