How to calculate area of Circle in Java?

[Aandaleeb]

Hi,
I am second year computer engineer student. As per our syllabus we have java language. In our last exam in java paper one program is asked like How to calculate Area of Circle? I used various method but unable to write right program. That's why I decide to take help of you. If you know how to write this program then please give me.

[Praetor]

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

public class CircleArea
 {

public static void main(String[] args)
 {
 
int r = 0;

System.out.println(" enter radius ");
try

{

BufferedReader br1 = new BufferedReader(new InputStreamReader(System.in));

r = Integer.parseInt(br1.readLine());

}

catch(NumberFormatException ne)

{

System.out.println("Invalid radius value" + ne);

System.exit(0);

}

catch(IOException ioe)

{

System.out.println("IO Error :" + ioe);

System.exit(0);

}
double a = Math.PI * r * r;

System.out.println("Area of  circle is " + a);

}
}

[Katty]

Hey I am not writing any program for you rather I give you logic behind it. You have to use following formula to calculate area of circle.

The formula is as follows:

Area of circle=Pi *r*r

where r=radius of circle,pi=3.14

You have to take radius from the user and save it in "r".

[kelfro]

import java.io.*;
class AreaOfCircle
{
  public static void main(String[] args){
    int radius=0;
           try{
        BufferedReader br2 = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter Radius of Circle  : ");
        radius = Integer.parseInt(br2.readLine());
        double area1 = java.lang.Math.PI*radius*radius;
        System.out.println("Area of Circle : "+area1);
        
      }
      catch(Exception e){
        System.out.println("Error : "+e);
      }        
  }
}

[Zecho]

This is one of the simplest and easiest progran.

class StaticCircle 
{
  public double r;
  double  pi=3.14;
  public void circle(double r)
  {
    this.r=r;

    }
    public double area()
    {
    double a1 = r*r;
    double piV= a1*pi;
    return piV;
    }
    public static void main(String[] args) 
    {
    StaticCircle  sCircle  = new StaticCircle ();
    sCircle.circle(10);
    double t = sCircle.area();
    System.out.println("The area is " + t);
  }
}