Username Validation using Java as per Client’s Requirement
By Priyam SurIn this Java programming tutorial, we will learn how to validate a username. For making it easy we have provided an easy example of username validation using Java.
USERNAME VALIDATION USING JAVA
Consider an employer is assigned to validate the username policy in his/her company’s internal networking platform developed in Java. According to that policy, a username is considered valid only if all the following constraints are satisfied:
- The username length must range between 7 to 20 characters otherwise, it will consider as an invalid username.
- The username is allowed to contain only underscores ( _ ) other than alphanumeric characters.
- The first character of the username must be an alphabetic character, i.e., [a-z] or [A-Z].
For example:
| Username | Validity |
| Alexa | Invalid |
| PriyamSur | Valid |
| Alexa_7878 | Valid |
| 1PriyamSur | Invalid |
| Priyam?Sur() | Invalid |
The format of Input:
- First input line: n, describing the total number of usernames.
- Next n lines: string describing the username.
Constraints of Input:
- 1<=n<=100
- The username consists of printable characters.
So, the format of Output is as given below:
- For each of the usernames, the output will print the string
Validif the username is valid as per our specified requirements. Otherwise, it will printInvalid. The program will check for each username and print if it is valid or invalid in each line.
Let’s take a look at the Java code below:
//Java8
import java.util.Scanner;
class UsernameValidator {
public static final String regularExpression = "^[a-zA-Z][a-zA-Z0-9_]{6,19}$";
}
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");
}
}
}
}Input:
8 Alexa Tamanna Samantha_21 2Priyam Sukanyam?10_2A JuliaZ007 Anjelina@007 _James007
Output:
Invalid Valid Valid Invalid Invalid Valid Invalid Invalid
Hope, you enjoyed this tutorial and it helped you to solve your problem.
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