3.23

#include<iostream>using namespace std;class cylinder{double r;double h;double vol;public:cylinder(double x,double y){r=x,h=y;}void vol_out(){vol=3.14*r*r*h;cout<<"该圆柱体的体积为："<<"\n"<<vol<<endl;}};int main(){cylinder c1(2,5);c1.vol_out();system("pause");return 0;}