This Java program is used to calculate the area of a circle.
import java.util.Scanner;
public class CircArea {
public static void main(String ag[]) {
int rad;
double pie = 3.14, ar;
Scanner s = new Scanner(System.in);
System.out.print("Enter radius of circle:");
rad = s.nextInt();
ar = pie * rad * rad;
System.out.println("Area of circle:" + ar);
}
}This program is used to calculate the area of a circle where the
radius will be fetched from user. So, first you have to import the
util package of Java so that you can use the Scanner class
in this program which will help programmers to fetch input from
users. Then define a class name CircArea. Inside the class
define the main() function. All Java program needs one main()
function from where it starts executing program. Next declare an
integer type variable rad which will hold the radius of
the circle and two double type variable pie and
ar, where pie will store the decimal value which is
3.14 and ar will be used to store the calculated area of
circle. Also define an object name s of
Scanner class using which the value will be fetched from input
device. Then System.out.println(); will be used to display a
message - " Enter radius of circle:". Then the statement rad =
s.nextInt(); will be used to fetch the value from
keyboard, and parse it to integer from string and store to variable
rad. Then calculating the result value of multiplication of pie
and rad * rad will get assigned to
ar variable.
Then the next System.out.println() will be used to display the
message - "Area of circle:" along with the calculated output which
is stored in the variable ar.
