4-8 定义一个 Dog 类，包含 age,weight 等属性，以及对这些属性操作的方法。实现并测试这个类。#include using namespace std;class Dog{public:void setAge(int a){age=a;}int getAge(){return age;}void setWeight(float w){weight=w;}float getWeight(){return weight;}private:int age;float weight;};void main(){Dog d;(3);(30);cout<<"小狗："<<()<<"岁，重"<<()<<"斤。"<#include <>using namespace std;class Rectangle{public:Rectangle(int xx1,int yy1,int xx2,int yy2){x1=xx1;y1=yy1;x2=xx2;y2=yy2;}float getArea(){return fabs(x2-x1)*fabs(y2-y1);}private:int x1,y1;int x2,y2;};void main(){Rectangle rec(0,0,10,20);cout<<"矩形面积："<<()<using namespace std;class Rectangle{public:Rectangle(int l,int w){length=l;width=w;}float getArea(){return length*width;}private:int length;int width;};void main(){Rectangle rec(10,20);cout<<"矩形面积："<<()<using namespace std;const float PI=;class Circle{public:Circle(float r){radius=r;}float getArea(){return radius*PI*PI;}private:float radius;};void main(){Circle c;cout<<"圆的面积："<<()<using namespace std;class Document{public:Document(char * n){strcpy(name,n);}void show(){cout<
