class Acl {

  public static boolean addResourcePrefixUser(Principal user, String identitySourceId) {
    checkNotNull(user);
    String userName = user.getUserResourceName();
    checkArgument(!Strings.isNullOrEmpty(userName), "userName can not be empty or null");
    if (userName.startsWith(IDENTITY_SOURCES_PREFIX)) {
      return false;
    }
    user.setUserResourceName(String.format(USER_RESOURCE_NAME_FORMAT, identitySourceId, userName));
    return true;
  }

  private  Acl(Builder builder);

}