I’m tired of this regex challenge. Is it still an interview topic, and how often do you write it at work now that AI can do this quickly?

It’s a nice challenge to combine regex syntax with problem-solving in Java. Mahadev Book ID Login

public static final String regularExpression = "^[A-Za-z][A-Za-z0-9_]{7,29}$";`

"^[A-Za-z]" → first char must be a letter.

"[A-Za-z0-9_]{7,29}" → remaining chars must be alphanumeric or _, length between 7 and 29.

Total length = 1 (first char) + [7–29] = 8–30 characters.

Anchors ^...$ ensure no extra characters sneak in.

import java.util.Scanner;

public class Solution { public static void main(String[] args) { Scanner sc = new Scanner(System.in); int n = Integer.parseInt(sc.nextLine()); // use nextLine() here

    String regex = "^[A-Za-z][A-Za-z0-9_]{7,29}$";

    for (int i = 0; i < n; i++) {
        String username = sc.nextLine(); 

        if (username.matches(regex)) {
            System.out.println("Valid");
        } else {
            System.out.println("Invalid");
        }
    }
    sc.close();
}

}

import java.io.; import java.util.;

public class Solution {

public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);

    int n = scanner.nextInt();
    scanner.nextLine();
    for(int i = 0; i<n; i++){
        String word = scanner.nextLine();
        if(word.matches("^[a-zA-Z][a-zA-Z0-9_]{7,29}$")) System.out.println("Valid");
        else System.out.println("Invalid");
    }
}

}