* it must be synchronized externally.
 * </p>
 * <p>
 * For thread-safe usage, wrap with {@link java.util.Collections#synchronizedMap(Map)}:
 * </p>
 * <pre>
 * Map&lt;K, V&gt; syncMap = Collections.synchronizedMap(new LruHashMap&lt;&gt;(100));
 * </pre>
 * <p>
 * Alternatively, for high-concurrency scenarios, consider implementing a custom

    return new SynchronizedMap<>(map, mutex);
  }

  private static class SynchronizedMap<K extends @Nullable Object, V extends @Nullable Object>
      extends SynchronizedObject implements Map<K, V> {
    transient @Nullable Set<K> keySet;
    transient @Nullable Collection<V> values;
    transient @Nullable Set<Map.Entry<K, V>> entrySet;

    SynchronizedMap(Map<K, V> delegate, @Nullable Object mutex) {

  }

  @VisibleForTesting
  static <K extends @Nullable Object, V extends @Nullable Object> Map<K, V> map(
      Map<K, V> map, @Nullable Object mutex) {
    return new SynchronizedMap<>(map, mutex);
  }

  private static class SynchronizedMap<K extends @Nullable Object, V extends @Nullable Object>
      extends SynchronizedObject implements Map<K, V> {
    transient @Nullable Set<K> keySet;

     * @param value the parameter value to store
     */
    public synchronized void putToInfoMap(final String key, final String value) {
        if (infoMap == null) {
            infoMap = Collections.synchronizedMap(new LinkedHashMap<>());
        }
        logger.debug("infoMap: {}={} => {}", key, value, infoMap);
        infoMap.put(key, value);
    }

    /**

    /**
     * Synchronized LRU cache for storing parent URL encodings.
     * Maps session+parent URL keys to their corresponding character encodings.
     */
    Map<String, String> parentEncodingMap = Collections.synchronizedMap(new LruHashMap<>(1000));

    /**
     * Gets the Fess configuration instance.
     *
     * @return the Fess configuration object
     */
    FessConfig getFessConfig();

    /**