Gender Marker (Medical / Governmental) Regex for Java

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching gender marker (medical / governmental), ported and verified for Java. Identity and credential patterns need both correctness and safety, since they're frequent targets for adversarial input. The snippet below is ready to drop into your Java project — whether you're validating in a Spring Boot controller, a Jakarta EE service, or a standalone utility class.

Java Implementation

// Gender Marker (Medical / Governmental)
// ReDoS-safe | RegexVault — Identity & PII > Biometric & Physical

import java.util.regex.Pattern;

public class GenderMarkerMedicalGovernmentalValidator {
    private static final Pattern PATTERN =
        Pattern.compile("^(?:M|F|X|O|U|N|NB|MALE|FEMALE|NON-BINARY|UNKNOWN|UNSPECIFIED|PREFER_NOT_TO_SAY|INTERSEX)$");

    public static boolean validate(String input) {
        return PATTERN.matcher(input).matches();
    }

    // Example
    public static void main(String[] args) {
        System.out.println(validate("M")); // true
    }
}

Test Cases

When to use this pattern

This pattern is drawn from the Identity & PII > Biometric & Physical category and carries a ReDoS-safe certification. That matters for Java developers because critical in Java applications since the JVM regex engine uses backtracking and is susceptible to ReDoS without careful pattern design. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

ICAO uses M/F/X for passports. HL7 FHIR uses M/F/O/U/N codes. Government documents vary: AU allows X (non-binary), UK driving licence adds a 5-month offset for female, CA federal documents allow X. The X gender marker is now recognized in many jurisdictions.