}

  Set<K> keySet;

  @Override
  public Set<K> keySet() {
    // does not impact recency ordering
    Set<K> ks = keySet;
    return (ks != null) ? ks : (keySet = new KeySet(this));
  }

  Collection<V> values;

  @Override
  public Collection<V> values() {
    // does not impact recency ordering
    Collection<V> vs = values;
    return (vs != null) ? vs : (values = new Values(this));
  }

                .concurrencyLevel(1)
                .ticker(ticker)
                .expireAfterAccess(1, NANOSECONDS));
    Segment<Object, Object> segment = map.segments[0];
    // TODO(fry): check recency ordering

    Object key = new Object();
    int hash = map.hash(key);
    Object value = new Object();
    AtomicReferenceArray<ReferenceEntry<Object, Object>> table = segment.table;

  /** Number of (unsynchronized) retries in the containsValue method. */
  static final int CONTAINS_VALUE_RETRIES = 3;

  /**
   * Number of cache access operations that can be buffered per segment before the cache's recency
   * ordering information is updated. This is used to avoid lock contention by recording a memento
   * of reads and delaying a lock acquisition until the threshold is crossed or a mutation occurs.
   *