用类求圆面积c++

#include<iostream>.
#include<math.h>
using namespace std;
class Circle
{
    public:
        double Transfer(double newr);
        double area();
    private:
        double r;                   
};
double Circle::Transfer(double newr)
{
    r=newr;
}
inline double Circle::area()
{
    cout<<r*r*3.14<<endl;
}
int main()
{
    Circle newcircle;
    double a;
    while(cin>>a)
    {
        newcircle.Transfer(a);
        newcircle.area();
    }
    return 0;
}

在用类时  记得类和结构体一样的地方就是class Circle不用加“（）”还有在后面要加“；”