# Valid Username Regular Expression | HackerRank Solution

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

Contents

## 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:

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
[email protected]
_Julia007``````

#### Sample Input

`````` Invalid
Valid
Valid
Invalid
Invalid
Valid
Invalid
Invalid``````

## Solution –Valid Username Regular Expressionin 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.