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
hassan says
October 26, 2014 at 6:39 PMWhy r we using static scanner sc? What’s Math.PI?
Ra's Al Ghul says
August 24, 2015 at 12:53 AMWhat do you think Math.PI is, you fucking idiot. It’s pi or 3.14.
hassan says
December 27, 2015 at 6:52 AMHey 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.
sanny says
February 28, 2016 at 11:24 PMthere is no stupid questions, there is only stupid answers.
sreekanth says
October 4, 2015 at 12:27 AM1.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.
riya says
March 8, 2016 at 12:37 PMi 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?
Imtiaz Ahmad says
March 22, 2016 at 6:35 PMHi 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.
chris says
April 5, 2016 at 4:51 PMHow do I round it off
Saron says
March 4, 2017 at 8:42 AMY we shouldn’t call the method can u explain in detail