return backingSet().contains(key);
    }

    @Override
    public @Nullable V get(@Nullable Object key) {
      return getOrDefault(key, null);
    }

    @Override
    public @Nullable V getOrDefault(@Nullable Object key, @Nullable V defaultValue) {
      if (Collections2.safeContains(backingSet(), key)) {
        @SuppressWarnings("unchecked") // unsafe, but Javadoc warns about it

    String CRAWLER_METADATA_CONTENT_EXCLUDES = "crawlerMetadataContentExcludes";

    Map<String, Object> propMap = new ConcurrentHashMap<>();

    String getOrDefault(String propertyKey, String defaultValue);

    //
    // system.properties
    //

    default void storeSystemProperties() {
        ComponentUtil.getSystemProperties().store();
    }

     * @return the maximum message length
     */
    protected int getMaxMessageLength(final FessConfig fessConfig) {
        try {
            return Integer.parseInt(fessConfig.getOrDefault("rag.chat.message.max.length", "4000"));
        } catch (final NumberFormatException e) {
            logger.warn("Invalid rag.chat.message.max.length config, using default 4000");
            return 4000;
        }

    if (value == null) {
      globalStatsCounter.recordMisses(1);
    } else {
      globalStatsCounter.recordHits(1);
    }
    return value;
  }

  @Override
  public @Nullable V getOrDefault(@Nullable Object key, @Nullable V defaultValue) {
    V result = get(key);
    return (result != null) ? result : defaultValue;
  }

  V getOrLoad(K key) throws ExecutionException {

    if (value == null) {
      globalStatsCounter.recordMisses(1);
    } else {
      globalStatsCounter.recordHits(1);
    }
    return value;
  }

  @Override
  public @Nullable V getOrDefault(@Nullable Object key, @Nullable V defaultValue) {
    V result = get(key);
    return (result != null) ? result : defaultValue;
  }

  V getOrLoad(K key) throws ExecutionException {

     *
     * @param index the index configuration name
     */
    protected void sendConfigFiles(final String index) {
        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        configListMap.getOrDefault(index, Collections.emptyList()).forEach(path -> {
            String source = null;
            final String filePath = indexConfigPath + "/" + index + "/" + path;
            final String dictionaryPath;