java的基础，求圆的面积和周长。

interface shape
{
public double getarea();
public double getperimeter();
public void printA();
}

class circle implements shape {
double radius;
public circle(double r) {
this.radius=r;
}

public double getarea() {
return 3.14*radius*radius;
}

public double getperimeter() {
return 2*3.14*radius;
}

public void printA()
{
System.out.println(getarea());
System.out.println(getperimeter());
}

}

class aa1 {
public void main(String args[]) {
circle i=new circle(2);
i.printA();
}
}

public class aa1 {
public static void main(Stri