# Area of a Circle in Java

The formula for calculating area of a circle is,

Area = PI * r * r, where PI is a constant and r is the radius of the circle.

The following sample Java program calculates area of a circle. The radius of the circle is taken as user input from command line. The default Java language package contains a Math class which the following program uses for the value of PI.

import java.util.Scanner; /** * Java program to calculate area of a circle * @author jj */ public class AreaOfCircle { public static void main(String[] args) { System.out.print("Enter radius of circle: "); Scanner sn = new Scanner(System.in); Double radius = sn.nextDouble(); Double area = Math.PI * radius * radius; System.out.println("Area = "+area); } }