Question

PLEASE INCLUDE COMMENTS

In java

Create a Java Program

• Add the following comments at the beginning of the file:
  • Your name.
  • The name of the class(es) used in the program.
  • The core concept (found below) for this lesson.
  • The date the program was written.
• Include a recursive method separate from the main method that will add together all of the even numbers between and including 1 and the value the user supplies. For instance, if the user enters 10 then the recursive method will return 2 + 4 + 6 + 8 + 10 = 30. If the user enters 5 then the recursive method will return 2 + 4 = 6.
• In the main method:
  • Ask the user for an integer. Call the recursive method, passing it the user input.
  • Include error handling for the input (the input must be an integer).
  • Display the original value and the result of the recursive method calculation. Include an appropriate output message.
  • Repeat the program until the user chooses to quit.

Answer 1

/*

*   Java program to add even numbers recurssively

*/

import java.util.Scanner;

import java.util.*;

// Declaration of class

class recSum{

    // main method execution starts from here

    public static void main(String[] args){

        // Declaration of variable

        int choice = 0;

        // Iterates while user input quit condition

        do{

            // promot message for user

            System.out.print("\nEnter number: ");

            int number = getInteger();              // call function

            // it checks for possitive integer no

            if(number > 0){

                recEvenSum(number, 0);

            }

            else{

                System.out.println("Enter Possitive no only");

            }

            // promot message for user

            System.out.println("\nPress 0 to continue, 1 to Quit");

            choice = getInteger();                  // call function

        }while(choice != 1);                        // checks for terminating condition

    }

    // this function return integer value input from user

    public static int getInteger(){

        // create object for scanner class

        Scanner i = new Scanner(System.in);

        int number = 0;

        

        // iterate while valid input

        for(boolean test = false; test == false;){

            try{

                number = i.nextInt();           // get input from console

                test = true;

                return number;                  // return to calling function

            }

            // throws error if input not integer

            catch(InputMismatchException e){

                System.out.println("Invalid input");

            }

            i.nextLine();                       // nextInt() function tripping on subsequent calls so its required

        }

        return number;

    }

    // recursive function for finding sum of even no's takes two parameters

    public static void recEvenSum(int number, int sum){

        // iterate while greater than 0

        if(number >= 0){

            // checks for even no

            if(number % 2 == 0){

                sum += number;                      // add number to sum

                recEvenSum(number - 2, sum);        // recursive call

            }else

                recEvenSum(number - 1, sum);

        }else{                                      // print final sum

            System.out.println("The recursive Even no's Sum: " + sum );

        }

    }

}