Valid Username Regular Expression | HackerRank Solution

Hello coders, today we are going to solve Valid Username Regular Expression HackerRank Solution in Java.

Valid Username Regular Expression

Problem

You are updating the username policy on your company’s internal networking platform. According to the policy, a username is considered valid if all the following constraints are satisfied:

  • The username consists of 8 to 10 characters inclusive. If the username consists of less than 8 or greater than 30 characters, then it is an invalid username.
  • The username can only contain alphanumeric characters and underscores (_). Alphanumeric characters describe the character set consisting of lowercase characters [a-z], uppercase characters [A-Z], and digits [0-9].
  • The first character of the username must be an alphabetic character, i.e., either lowercase character [a-z] or uppercase character [A-Z].

For example:

UsernameValidity
JuliaINVALID; Username length < 8 characters
SamanthaVALID
Samantha_21VALID
1SamanthaINVALID; Username begins with non-alphabetic character
Samantha?10_2AINVALID; ‘?’ character not allowed

Update the value of regularExpression field in the UsernameValidator class so that the regular expression only matches with valid usernames.

Input Format

The first line of input contains an integer n, describing the total number of usernames. Each of the next n lines contains a string describing the username. The locked stub code reads the inputs and validates the username.

Constraints

  • 1 <= n <= 100
  • The username consists of any printable characters.

Output Format

For each of the usernames, the locked stub code prints Valid if the username is valid; otherwise Invalid each on a new line.

Sample Input

 8
 Julia
 Samantha
 Samantha_21
 1Samantha
 Samantha?10_2A
 JuliaZ007
 Julia@007
 _Julia007

Sample Input

 Invalid
 Valid
 Valid
 Invalid
 Invalid
 Valid
 Invalid
 Invalid

Solution – Valid Username Regular Expression in Java

import java.util.Scanner;
class UsernameValidator {
    /*
     * Write regular expression here.
     */
    public static final String regularExpression = "^[A-Za-z]\\w{7,29}$";
}


public class Solution {
    private static final Scanner scan = new Scanner(System.in);
    
    public static void main(String[] args) {
        int n = Integer.parseInt(scan.nextLine());
        while (n-- != 0) {
            String userName = scan.nextLine();

            if (userName.matches(UsernameValidator.regularExpression)) {
                System.out.println("Valid");
            } else {
                System.out.println("Invalid");
            }           
        }
    }
}

Disclaimer: The above Problem ( Valid Username Regular Expression ) is generated by Hacker Rank but the Solution is Provided by CodingBroz. This tutorial is only for Educational and Learning Purpose.

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