synchronized (lock) {
      return cachingHashMap.containsKey(key) && !isExpired(cachingHashMap.get(key));
    }
  }

  @Override
  public boolean containsValue(@Nullable Object value) {
    synchronized (lock) {
      for (Timestamped<V> val : cachingHashMap.values()) {
        if (val.getValue().equals(value)) {
          if (!isExpired(val)) {
            return true;
          }
        }
      }

        if (session == null) {
            if (logger.isDebugEnabled()) {
                logger.debug("Session not found. sessionId={}", sessionId);
            }
            return null;
        }
        if (isExpired(session)) {
            sessionCache.remove(sessionId);
            if (logger.isDebugEnabled()) {

    V value = entry.getValueReference().get();
    if (value == null) {
      return null;
    }

    if (isExpired(entry, now)) {
      return null;
    }
    return value;
  }

  // expiration

  /** Returns true if the entry has expired. */
  boolean isExpired(ReferenceEntry<K, V> entry, long now) {
    checkNotNull(entry);

    V value = entry.getValueReference().get();
    if (value == null) {
      return null;
    }

    if (isExpired(entry, now)) {
      return null;
    }
    return value;
  }

  // expiration

  /** Returns true if the entry has expired. */
  boolean isExpired(ReferenceEntry<K, V> entry, long now) {
    checkNotNull(entry);