实例化

#include <iostream>
using namespace std
    class Box
    {
        public:
        double length;
        double breadth;
        double height;
        double getVolume(void);
        void setLength(double len);
        void setBreadth(double bre);
        void setHeight(double hei);
    };
double Box::getVolume()
{
    return length*breadth*height;
}
void Box::setLength(double len)
{
    length=len;
}
void Box::setBreadth(double bre)
{
    breadth=bre;
}
void Box::setHeight(double hei)
{
    height=hei;
}
int main(){
    Box box1;
    box1.length = 5.0;
    Box* pBox2 = new Box();
    (*pBox2).length = 4.0;
    pBox2->height = 50.0;
   double length = pBox2->getVolume();
    delete pBox2;
}

get、set 函数

通过private实现

构造函数

析构函数