class Circle
{
    private float r;
    private final double PI = 3.1415926;
    
    public Circle(float x)
    {
        r = x;
    }
    
    public double circum()
    {
        return 2 * PI * r;
    }
    
    public double area()
    {
        return PI * r * r;
    }
}
public class UseCircle
{
    public static void main(String[] args)
    {
        Circle yuan = new Circle(3);
        double a = yuan.circum();
        double b = yuan.area();
        System.out.println("周长为:" + a);
        System.out.println("面积为:" + b);
    }
}