Read a $3-$character string from input into variable userString. Declare a Boolean variable isValid and assign isValid with true if userString only contains digits. Otherwise, assign isValid with false.

Ex: If the input is $342,$ then isValid is assigned with true, so the output is:

Good string

Ex: If the input is d$69,$ then isValid is assigned with false, so the output is:

Bad string

Note: Use userString $=$ scnr$.$nextLine$()$ to read the entire line from input into userString.

import java.util.Scanner;

public class StringChecker $\{$

public static void main$($String$[]$ args$)\{$

Scanner scnr $=$ new Scanner$($System$.$in$)$;

String userString;

$/*$ Your code goes here $*/$

if $($isValid$)\{$

System.out.println$("$Good string"$)$;

$\}$

else $\{$

System.out.println$("$Bad string"$)$;

$\}$

$\}$

$\}$