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Java Program to calculate area and circumference of circle

By Chaitanya Singh | Filed Under: Java Examples

In this tutorial we will see how to calculate area and circumference of circle in Java. There are two ways to do this:

1) With user interaction: Program will prompt user to enter the radius of the circle
2) Without user interaction: The radius value would be specified in the program itself.

Program 1:

/**
 * @author: BeginnersBook.com
 * @description: Program to calculate area and circumference of circle
 * with user interaction. User will be prompt to enter the radius and 
 * the result will be calculated based on the provided radius value.
 */
import java.util.Scanner;
class CircleDemo
{
   static Scanner sc = new Scanner(System.in);
   public static void main(String args[])
   {
      System.out.print("Enter the radius: ");
      /*We are storing the entered radius in double
       * because a user can enter radius in decimals
       */
      double radius = sc.nextDouble();
      //Area = PI*radius*radius
      double area = Math.PI * (radius * radius);
      System.out.println("The area of circle is: " + area);
      //Circumference = 2*PI*radius
      double circumference= Math.PI * 2*radius;
      System.out.println( "The circumference of the circle is:"+circumference) ;
   }
}

Output:

Enter the radius: 1
The area of circle is: 3.141592653589793
The circumference of the circle is:6.283185307179586

Program 2:

/**
 * @author: BeginnersBook.com
 * @description: Program to calculate area and circumference of circle
 * without user interaction. You need to specify the radius value in 
 * program itself.
 */
class CircleDemo2
{
   public static void main(String args[])
   {
      int radius = 3;
      double area = Math.PI * (radius * radius);
      System.out.println("The area of circle is: " + area);
      double circumference= Math.PI * 2*radius;
      System.out.println( "The circumference of the circle is:"+circumference) ;
   }
}

Output:

The area of circle is: 28.274333882308138
The circumference of the circle is:18.84955592153876

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Comments

  1. hassan says

    October 26, 2014 at 6:39 PM

    Why r we using static scanner sc? What’s Math.PI?

    Reply
    • Ra's Al Ghul says

      August 24, 2015 at 12:53 AM

      What do you think Math.PI is, you fucking idiot. It’s pi or 3.14.

      Reply
      • hassan says

        December 27, 2015 at 6:52 AM

        Hey asshole!

        It’s good to see you bashing your fabulous vocabulary and knowledge at others. But I was merely confused about the function. So just STFU and get lost instead of swearing at others, you filthy pig. Never asked you for your opinion so stop acting like a fucking retard. Get a life.

        Reply
      • sanny says

        February 28, 2016 at 11:24 PM

        there is no stupid questions, there is only stupid answers.

        Reply
  2. sreekanth says

    October 4, 2015 at 12:27 AM

    1.Write a program to create an integer array that allows user to enter numbers , display the numbers in forward and reverse order then find their sum and average. Also display the element at each index.

    Reply
  3. riya says

    March 8, 2016 at 12:37 PM

    i do not have much programming knowledge.
    can someone tell me the use of following lines?

    1> Scanner sc = new Scanner(System.in);
    why we use system.in ??? what does it mean? and what is it’s use?

    2> double radius = sc.nextDouble();
    Why nextDouble? what does it mean? and what is it’s use?

    Reply
    • Imtiaz Ahmad says

      March 22, 2016 at 6:35 PM

      Hi Dear! Riya
      System.in is an InputStream which is typically connected to keyboard input of console programs. System.in is not used as often since data is commonly passed to a command line Java application via command line arguments, or configuration files. In applications with GUI the input to the application is given via the GUI. This is a separate input mechanism from Java IO.

      Reply
  4. chris says

    April 5, 2016 at 4:51 PM

    How do I round it off

    Reply
  5. Saron says

    March 4, 2017 at 8:42 AM

    Y we shouldn’t call the method can u explain in detail

    Reply

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