Question

Ok, so I know this is a noob question but I am having trouble getting this code to work. What the code is supposed to do is give you the diamter when you input the radius. I know my code is probably butchered but what am I doing wrong and why because I am trying to learn.

import java.util.Scanner;

public class Circle{

Scanner dd = new Scanner(ystem.in);

System.out.println("Whats is the radius?");
double r = dd.nextDouble();

public Circle(double r){

    radius = r;
}

public double diameter(){

    double d = radius * 2;
    return d;
}
}

public class Tester{

public static void main(String args[]){

    Circle cir1 = new Circle(35.5);
    System.out.println(Circle.diameter)
}
}

Answer 1

You must put you code in a method. This block will cause an error :

Scanner dd = new Scanner(System.in);

System.out.println("Whats is the radius?");
double r = dd.nextDouble();

Next, in your main, you do Circle cirl = new Circle(35.5) and on the next line, you call Circle.diameter. You should call the diameter from you new instance as so cirl.diameter().

You could try something like this instead

import java.util.Scanner;

public class Circle{

    private double radius;

    public Circle(double r){

        radius = r;
    }

    public double diameter(){

        double d = radius * 2;
        return d;
    }

    public static void main(String args[]){

        Scanner dd = new Scanner(System.in);

        System.out.println("Whats is the radius?");
        double r = dd.nextDouble();
        Circle cir1 = new Circle(r);
        System.out.println(cir1.diameter())
    }
}