solicitar el radio de un circulo

import java.util.Scanner;
public class JavaApplication1 {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double r;
        System.out.println("What is the radius of your circle?");
        r = scan.nextDouble();
        double circum = 2 * Math.PI * r;
        System.out.println("The circumference of your circle is " + circum);
    }
}