使用默认参数的构造函数

#include <iostream>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */
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(int argc, char** argv) {
    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;
}