TUTORIAL DO JAAS esta dando erro

...
    private boolean commitSucceeded = false;
    private boolean succeeded = false;
    private User user;
    private Set roles = new HashSet();
    protected Subject subject;
    protected CallbackHandler callbackHandler;
    protected Map sharedState;
    private String dataSourceName;
    private String sqlUser;
    private String sqlRoles;
....


    public boolean commit() throws LoginException {
        // adiciona o usuario no principals
        if (user != null && !subject.getPrincipals().contains(user)) {
            subject.getPrincipals().add(user);
        }
        // adiciona as roles no principals
        if (roles != null) {
            Iterator it = roles.iterator();
            while (it.hasNext()) {
                Role role = (Role) it.next();
                if (!subject.getPrincipals().contains(role)) {                   
                    subject.getPrincipals().add(role); ----------------------- AQUI ----------------------------------
                }
            }
        }

        commitSucceeded = true;
        return true;
    }