@Override
      protected @Nullable Integer computeNext(Integer previous) {
        return (previous == last) ? null : previous * 2;
      }
    };
  }

  private static class EmptyAbstractSequentialIterator<T> extends AbstractSequentialIterator<T> {

    EmptyAbstractSequentialIterator() {
      super(null);
    }

    @Override
    protected T computeNext(T previous) {

     * Delays the crawling process before processing a URL.
     */
    protected abstract void delayBeforeProcessing();

    /**
     * Delays the crawling process after processing a URL.
     */
    protected abstract void delayAfterProcessing();

    /**
     * Delays the crawling process when there are no URLs in the queue.
     */
    protected abstract void delayAtNoUrlInQueue();

    /**

    protected String getTestSeries() {
        String className = getClass().getPackage().getName();

        return className.substring(className.lastIndexOf('.') + 1);
    }

    protected File projectFile(String name) {
        return projectFile("maven", name);
    }

    protected File projectFile(String groupId, String artifactId) {

    //                                                                           =========
    /** createdTime */
    protected Long createdTime;

    /** expiredTime */
    protected Long expiredTime;

    /** name */
    protected String name;

    /** sessionId */
    protected String sessionId;

    // [Referrers] *comment only

    //                                                                           =========
    /** crawlingInfoId */
    protected String crawlingInfoId;

    /** createdTime */
    protected Long createdTime;

    /** key */
    protected String key;

    /** value */
    protected String value;

    // [Referrers] *comment only

     * @param lang The language.
     */
    public void addLang(final String lang) {
        languages.add(lang);
    }

    @Override
    protected String getValidationError() {
        return null;
    }

    @Override
    protected void processRequest(final Client client, final Deferred<SuggestResponse> deferred) {
        final SearchRequestBuilder builder = client.prepareSearch(index);

    protected boolean includeAware;

    /**
     * A map of attributes.
     */
    protected final Map<String, Object> attributeMap = new HashMap<>();

    /**
     * A map of features.
     */
    protected final Map<String, String> featureMap = new HashMap<>();

    /**
     * A map of field rules.
     */
    protected Map<String, String> fieldRuleMap = new LinkedHashMap<>();

    private static final long serialVersionUID = 1L;

    /** The environment for LDAP connection. */
    protected Hashtable<String, String> env;

    /** The name of the user. */
    protected String name;

    /** The permissions of the user. */
    protected String[] permissions = null;

    /**
     * Constructs a new LDAP user.
     *
     * @param env The environment for LDAP connection.

     */
    public RoleTypeService() {
        super();
    }

    /**
     * The behavior for role types.
     */
    @Resource
    protected RoleTypeBhv roleTypeBhv;

    /**
     * The Fess configuration.
     */
    @Resource
    protected FessConfig fessConfig;

    /**
     * Gets a list of role types based on the pager.
     * @param roleTypePager The pager for role types.

     *
     * @param buf the string buffer to append to
     * @param key the key name
     * @param supplier the value supplier
     * @return the updated buffer
     */
    protected StringBuilder append(final StringBuilder buf, final String key, final Supplier<Object> supplier) {
        final StringBuilder tempBuf = new StringBuilder();
        tempBuf.append('"').append(key).append("\":");
        try {