Question

Write a method that accepts an integer argument and returns the sum of all the integers from 1 up to (and including) the number passed as an argument. For example, if 3 is passed as an argument, the method will return the sum of 1+2+3, which is 6. Use recursion to calculate the sum. Test your method in main by prompting the user to enter a positive integer to sum up to. Provide input validation so that only positive values are accepted.

Answer 1

Answer:

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Explanation:

import java.util.*;

public class Main {

       public static int sumOfNumbers(int n)

       {

               if(n==0) return 0;

               else

               return n+sumOfNumbers(n-1);

       }

       public static void main(String[] args) {

               Scanner sc=new Scanner(System.in);

               int n;

               while(true)

               {

                       System.out.println("Enter a number :");

                       n=sc.nextInt();

                       if(n<=0)

                       System.out.println("Enter a positive number ");

                       else

                       break;

               }

               System.out.println("Sum of all numbers upto "+n+" is :"+sumOfNumbers(n));

       }

}