Program to Calculate the Area of a circle

Input

1. Radius of the circle in integer value (example radius=4)

Program Code

package programs.java4newbie.com;

/*
 This program accepts an integer value for radius of circle
 and then return the area of the circle.
 */

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

public class CircleArea {

 public static void main(String[] args) {

 float 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 = Float.parseFloat(br.readLine());
 }
 // if invalid value was entered
 catch (NumberFormatException nfe) {
 System.out
 .println("Invalid value for radius entered, please try again with a valid value ");
 System.exit(0);
 } catch (IOException ioe) {
 System.out.println("IO Error ");
 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

Please enter radius of a circle
5
Area of a circle is 78.53981633974483