Question

Write a program that asks the user for a positive integer value. The program should use a loop to get the sum of all even integers from 0 up to the number entered, and then display the sum. For example, if the user enters 11, the loop will find the sum of 2, 4, 6, 8, and 10. Input validation: Do not accept a negative number or 0 from user input

Answer 1

import java.io.*;

public class GFG {

   // Returns true if s is

   // a number else false

   static boolean isNumber(String s)

   {

       for (int i = 0; i < s.length(); i++)

           if (Character.isDigit(s.charAt(i)) == false)

               return false;

       return true;

   }

   // Driver code

   static public void main(String[] args)

   {

       // Saving the input in a string

       String str = "6790";

       // Function returns 1 if all elements

       // are in range '0 - 9'

       if (isNumber(str))

           System.out.println("Integer");

       // Function returns 0 if the

       // input is not an integer

       else

           System.out.println("String");

   }

}