Valid Username Regular Expression

Valid Username Regular Expression:

Problem Description:

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 30 characters inclusive. If the username consists of less than  or greater than 8 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].

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 , describing the total number of usernames. Each of the next  lines contains a string describing the username. The locked stub code reads the inputs and validates the username.

Constraints

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 0:

8

Julia

Samantha

Samantha_21

1Samantha

Samantha?10_2A

JuliaZ007

Julia@007

_Julia007

Sample Output 0:

Invalid

Valid

Valid

Invalid

Invalid

Valid

Invalid

Invalid

Solution:

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");

            }           

        }

    }

}

Reference:Valid Username Regular Expression

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