3.22：
#include<iostream>using namespace std;class circle{public:double radius;double s;void area();};void circle::area(){ cout<<"radius is "<<radius<<endl; s=radius*radius*3.14; cout<<"area is "<<s<<endl;}int main(){ circle one; one.radius=2.0; one.area(); return 0;}3.23：
#include<iostream>using namespace std;class cylinder{public:double v;cylinder(double r,double h);private:double radius;double high;};cylinder::cylinder(double r,double h){ radius=r; high=h; v=r*r*h*3.14; cout<<"radius is "<<r<<endl; cout<<"high is "<<h<<endl; cout<<"vol is "<<v<<endl;}int main(){ cylinder one(2.0 , 2.0); return 0;}3.24：
#include<iostream>using namespace std;class date{public:int y,m,d; date(int y,int m,int d); void printdate(); void getyear(int y); void getmonth(int m); void getday(int d);private:int year; int month; int day;}; date::date(int y,int m,int d){ year=y; month=m; day=d; } void date::printdate(){ cout<<"日期是："<<year<<"年"<<month<<"月"<<day<<"日"<<endl;}void date::getyear(int y){year=y; cout<<"年："<<year<<endl;}void date::getmonth(int m){month=m; cout<<"月："<<month<<endl;}void date::getday(int d){day=d;cout<<"日："<<day<<endl;}int main(){ date d1(2010,6,8); d1.printdate(); date d2(2015,7,15); d2.printdate(); date d3(d1); d3.printdate(); d2.getyear(2023); d2.getmonth(8); d2.getday(6); return 0;}
，三亚呀——赴一个蓝天碧海。
