Write a Program Area of Circle in Java - Technology369kk

 Area of Circle : 

In this post we are discussing about Area of Circle in Java but Rules 2 for beginner and Advance. 

Program : 

import java.util.*; // It it mandatory for both rules >>follow up rules 2 explanation

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

Rule 1: Using BufferedReader

class CircleArea{

    public static void main(String arg[]){

        int raduis = 0;

        System.out.println("Please Enter Raduis of a Circle: ");

        try{

            // get the raduis from console

            BufferedReader br= new

            BufferedReader(new InputStreamReader(System.in));

            raduis = Integer.parseInt(br.readLine());

        }

        // if invailed value was entered

        catch(NumberFormatException ne){

            System.out.println("Invailed raduis value"+ne);

            System.exit(0);

        }

        catch(IOException ioe){

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

            System.exit(0);

        }

        double area = Math.PI * raduis* raduis;

        System.out.println("Area of Circle is:"+ area);

    }

}

Explanation:  

• BufferReader and InputStramReader: 

• BufferedReader reads input more efficiently. 
• InputStramReader(System.in)  converts the byte stream(Keyboard input ) to character stream. 

• Error Handling: 
• NumberFormatException:  Catches invalid numeric input( e.g user enters "abc" instead of a number) 
• IOExecption:  Handles I/O errors during input reading. 

• Calculation: Uses Math.PI for accurate value of π

Rule 2: Using Scanner

class CircleArea1{

    public static void main(String arg[]){

        int raduis;

        System.out.println("Please Enter Raduis of a Circle: ");

        Scanner in = new Scanner(System.in);

        raduis = in.nextInt();

        double area = 3.14 * raduis*raduis;

        System.out.println("Area of Circle is :"+ area);

    }

}

Explanation:

• Scanner
• Simple than BufferedReader.
• nextInt() directly reads an integer, reducing the need for parseInt.
• Calculation: 
• Uses 3.14 as an approximations for PIE
• No Explicit Error Handling:
• If invalid input (e.g., non-integer) is provided, the program will throw an exception without catching it. You can improve it by wrapping nextInt() in a try-catch block for robustness.

Key Differences:

BufferedReader:

• Better for reading large input or multiple lines.
• Requires explicit conversion for numeric data.
• Needs IOException handling.

Scanner:

• Easier to use for simple, interactive input.
• Direct methods like nextInt() simplify data retrieval.
• No need for explicit IOException handling but prone to runtime errors for invalid input.