构造函数使用代码：
#include <iostream>
using namespace std;
class Rec
{const int length;int width;
public:Rec():length(10){cout << "Rec无参构造函数" << endl;};Rec(int a,int b):length(a),width(b){cout << "Rec有参构造函数" << endl;};void set_length(int l);void set_width(int w);int get_length();int get_width();void show();
};class Cir
{int &r;
public:Cir(int &a):r(a){cout << "Cir有参构造函数" << endl;};void set_r(int r); //设置私有属性r的值void show(double PI=3.14); //参数有默认值3.14
};class Car //类名首字母一般大小
{string color;string brand;int speed;
public:Car(){cout << "Car无参构造函数" << endl;};Car(string a,string b,int c):color(a),brand(b),speed(c){cout << "Car有参构造函数" << endl;};void set(string c,string b,int s);void display();void acc(int a);
};
int main()
{Rec a;int age=100;Rec b(age,22.2);int cc=8;Cir c(cc);Car s;Car ss("黑曜金","迈巴赫",200);Car *p=new Car[4];
}
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