An example case for the UnixSystem.java failure to retrieve uid, gid and groups if the user has no username

UnixSystemNamelessError.java

public class UnixSystemNameless {

    public static void main(String[] args) {
        final var unixSystem = new com.sun.security.auth.module.UnixSystem();
        System.out.printf("username: %s%n", unixSystem.getUsername());
        System.out.printf("uid: %d%n", unixSystem.getUid());
        System.out.printf("gid: %d%n", unixSystem.getGid());
        System.out.printf("groups: %s%n", java.util.Arrays.toString(unixSystem.getGroups()));
    }

}