This example shows how to validate a Username string in Java using regular expression with Regex Pattern and Matcher validation.
Username Regular Expression Pattern: ^[a-z0-9_-]{3,15}$
Description:
^ # Start of the line
[a-z0-9_-] # Match characters and symbols in the list, a-z, 0-9, underscore, hyphen
{3,15} # Length at least 3 characters and maximum length of 15
$ # End of the line
Example:
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import java.util.regex.Matcher; import java.util.regex.Pattern; public class UsernameValidator { private Pattern pattern; private Matcher matcher; private static final String USERNAME_PATTERN = "^[a-z0-9_-]{3,15}$"; public UsernameValidator() { pattern = Pattern.compile(USERNAME_PATTERN); } /** * Validate username with regular expression * @param username username for validation * @return true valid username, false invalid username */ public boolean validate(final String username) { matcher = pattern.matcher(username); return matcher.matches(); } } |