以下为成员变量初始化与构造函数的实例

#include <iostream>
using namespace std;
class demo
{
public:
    demo(){x=0;cout<<"demo的默认构造函数！"<<x<<endl;}
    demo(int i){x=i;cout<<"demo的带一个参数的构造函数!"<<x<<endl;}
    ~demo(){cout<<"demo的默认析构函数"<<x<<endl;}
    int get(){return x;}
    void set(int i){x=i;}
private:
    int x;
};
class rectangle
{
public:
    rectangle(){x=1000;cout<<"rectangle的默认构造函数"<<x<<endl;}
    rectangle(int i,int j,int k):x(i),width(j),length(k)
    {
        cout<<"rectangle的三个参数的构造函数！"<<'/t'<<length.get()*width.get()<<endl;
    }
    ~rectangle(){cout<<"rectangle的默认析构函数"<<'/t'<<x<<endl;}
    int area(){return length.get()*width.get();}
private:
    int x;
    demo length;
    demo width;

};
int main()
{
    rectangle a(100,200,300);
    return 0;
}