This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.
package com.mathlearning.util;
public class UsernameValidator {
public static boolean isValid(String username) {
if (username == null || username.length() < 3 || username.length() > 20) {
return false;
}
return username.matches("^[a-zA-Z0-9_]+$");
public static String getRequirements() {
return "用户名要求: 3-20位，只能包含字母、数字和下划线";
