String function "CharAt" storing and displaying numeric values in "char"

Question

Ok guys so i'm using this string function "charAT" to store charater variable to store in char r. But we know user can input anything. When user enters a numeric value like 123 or 5 or anything charAt is storing that in char variable r. Exception should have come but it didn't. How is char variable able to hold a numeric value. How can i fix this? i want "r" to hold only char values and want the exception to occur if user inputs the numeric value.

package string;

import java.util.Scanner;

public class Example 
{

Scanner s1;
String str;
char r;

Example()
{
  s1 = new Scanner(System.in);
}

void display()
{
    while(true)
    {
    try {

    System.out.println("Please enter the grade");
    str = s1.nextLine();
    r = str.charAt(0);
    System.out.println("The grade is "+ r);
    break;
    }
    catch(Exception e)
    {
        System.out.println("you have entered an invalid input. Please try again \n");
    }
    }
}

public static void main(String[] args)
{
    new Example().display();
}
}

Answer 1

In Java the value of String and char can also accept numeric values. So if you enter 123 as input then the String will be "123" and the char will be 1. If you only want to get alphabets as input then you can do it using the hasNext method in the Scanner class of Java. This will use a Regular Expression such as [A-Za-z] to make sure only alphabets can be given as input.

while(true)
{
    try
    {
        System.out.println("Please enter the grade");
        while (!s1.hasNext("[A-Za-z]+")) {
            System.out.println("you have entered an invalid input. Please try again \n");
            s1.next();
        }
        str = s1.next();
        r = str.charAt(0);
        System.out.println("The grade is "+ r);
        break;
    }
    catch (Exception e)
    {
        System.out.println("There was an exception \n");
    }
}