The user is first prompted to enter a radius. Then the circumference and area of the circle are calculated, rounded and output to the screen.
import java.util.Scanner;
class CircumferenceCircularArea {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
double r, area, circumference;
System.out.print("Please enter radius: ");
r = reader.nextDouble();
reader.close();
// calculation of circumference
circumference = 2 * Math.PI * r;
// calculation of circular area
// Math.pow(base, exponent): Returns base raised to the power exponent
area = Math.PI * Math.pow(r, 2);
System.out.println("Circumference: " + String.format("%1.2f", circumference));
System.out.println( "Circular Area: " + String.format("%1.2f", area));
}
}
Please enter radius: 4.5
Circumference: 28.27
Circular Area: 63.62
import java.util.Scanner;
imports the Scanner
class from the java.util
package. This class is used to read user input from the console.
class CircumferenceCircularArea
declares a class named CircumferenceCircularArea
.
public static void main(String[] args)
is the main method of the program where the execution starts. It takes an array of strings as a parameter (although it is not used in this program).
The following lines declare variables:
Scanner reader = new Scanner(System.in);
double r, area, circumference;
Here, reader
is an instance of the Scanner
class that is used to read user input. r
is a double variable to store the radius entered by the user, and area
and circumference
are double variables to store the calculated values.
System.out.print("Please enter radius: ");
displays a prompt message asking the user to enter the radius.
r = reader.nextDouble();
reads a double value entered by the user using the nextDouble()
method of the Scanner
class. The value entered by the user is stored in the r
variable.
reader.close();
closes the Scanner
object to release system resources after reading the user input.
circumference = 2 * Math.PI * r;
calculates the circumference of the circle using the formula 2 * π * r
, where Math.PI
represents the mathematical constant π.
area = Math.PI * Math.pow(r, 2);
calculates the circular area using the formula π * r^2
. The Math.pow(base, exponent)
function is used to raise r
to the power of 2.
The following lines print the calculated values:
System.out.println("Circumference: " + String.format("%1.2f", circumference));
System.out.println("Circular Area: " + String.format("%1.2f", area));
The System.out.println()
statements display the calculated circumference and circular area values. The String.format("%1.2f", value)
is used to format the double values with two decimal places before displaying them.