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

public class Circle {
    public static void main(String[ ] args){
        int radius = 0;
        System.out.println("Enter radius of a circle : ");
        try
        {
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            radius = Integer.parseInt(br.readLine());
        }
        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);
        }
        radius = 5;
        double perimeter = 2 * Math.PI * radius;
        double area = Math.PI * radius * radius;

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

        }
}
- See more at: http://www.hubberspot.com/2012/03/java-source-code-how-to-calculate-area.html#sthash.U4rtCVaL.dpuf