/**
     * Calculates the document expiration date based on crawling configuration.
     * If the config has a timeToLive value, calculates expiration from current time.
     * Otherwise, returns the stored document expiration time.
     *
     * @param config the crawling configuration containing time-to-live settings
     * @return the document expiration date, or null if no expiration is set
     */

   * value after the specified time has passed. Subsequent calls to {@code get()} return the cached
   * value if the expiration time has not passed. After the expiration time, a new value is
   * retrieved, cached, and returned. See: <a
   * href="http://en.wikipedia.org/wiki/Memoization">memoization</a>
   *

   * value after the specified time has passed. Subsequent calls to {@code get()} return the cached
   * value if the expiration time has not passed. After the expiration time, a new value is
   * retrieved, cached, and returned. See: <a
   * href="http://en.wikipedia.org/wiki/Memoization">memoization</a>
   *

        private final long expiration;

        /**
         * Constructs StateData with nonce and expiration.
         * @param nonce The nonce value.
         * @param expiration The expiration timestamp.
         */
        public StateData(final String nonce, final long expiration) {
            this.nonce = nonce;
            this.expiration = expiration;
        }

        /**

     */
    public void setMaxCacheSize(final long maxCacheSize) {
        this.maxCacheSize = maxCacheSize;
    }

    /**
     * Sets the cache expiration time after write in milliseconds.
     *
     * @param cacheExpireAfterWrite the expiration time in milliseconds
     */
    public void setCacheExpireAfterWrite(final long cacheExpireAfterWrite) {
        this.cacheExpireAfterWrite = cacheExpireAfterWrite;
    }

 * modification checking, and integration with the Fess search engine backend.
 *
 * <p>Key features include:</p>
 * <ul>
 * <li>Incremental crawling support with last-modified timestamp checking</li>
 * <li>Document expiration handling</li>
 * <li>Child URL extraction and queueing</li>
 * <li>Integration with Fess configuration and permission systems</li>
 * <li>Client selection based on URL patterns</li>
 * </ul>
 *
 * @see CrawlerThread

     */
    public PopularWordHelper() {
        // Default constructor
    }

    /**
     * Initializes the PopularWordHelper after dependency injection.
     * Sets up the cache with configured size and expiration settings.
     */
    @PostConstruct
    public void init() {
        if (logger.isDebugEnabled()) {
            logger.debug("Initialize {}", this.getClass().getSimpleName());
        }

 * <i>not</i> include cache contents, but only configuration.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/CachesExplained">caching</a> for a higher-level
 * explanation.
 *
 * @param <K> the most general key type this builder will be able to create caches for. This is
 *     normally {@code Object} unless it is constrained by using a method like {@link

    public void setThumbnailTaskQueueSize(final int thumbnailTaskQueueSize) {
        this.thumbnailTaskQueueSize = thumbnailTaskQueueSize;
    }

    /**
     * Sets the expiration time for no-image placeholder files.
     *
     * @param noImageExpired the expiration time in milliseconds
     */
    public void setNoImageExpired(final long noImageExpired) {
        this.noImageExpired = noImageExpired;
    }

    /**

      }
    };

    abstract Equivalence<Object> defaultEquivalence();
  }

  /**
   * Implementation for the EntryIterator, which is used to build Key and Value iterators.
   *
   * <p>Expiration is only checked on hasNext(), so as to ensure that a next() call never returns
   * null when hasNext() has already been called.
   */
  private final class EntryIterator implements Iterator<Entry<K, V>> {