Java Source - Calculate Circle Area

---

    /*
 Calculate Circle Area using Java Example
 This Calculate Circle Area using Java Example shows how to calculate
 area of circle using it's radius.
 */

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class CalculateCircleAreaExample {

    public static void main(String[] args) {

        int radius = 0;
        System.out.println("Please enter radius of a circle");

        try {
            //get the radius from console
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            radius = Integer.parseInt(br.readLine());
        } //if invalid value was entered
        catch (NumberFormatException ne) {
            System.out.println("Invalid radius value" + ne);
            System.exit(0);
        } catch (IOException ioe) {
            System.out.println("IO Error :" + ioe);
            System.exit(0);
        }

        /*
         * Area of a circle is
         * pi * r * r
         * where r is a radius of a circle.
         */

        //NOTE : use Math.PI constant to get value of pi
        double area = Math.PI * radius * radius;

        System.out.println("Area of a circle is " + area);
    }
}

---

    /*
    Output of Calculate Circle Area using Java Example would be
    Please enter radius of a circle
    19
    Area of a circle is 1134.1149479459152
    */

---