final AtomicInteger readCount = new AtomicInteger();

    /**
     * A queue of elements currently in the map, ordered by write time. Elements are added to the
     * tail of the queue on write.
     */
    @GuardedBy("this")
    final Queue<ReferenceEntry<K, V>> writeQueue;

    /**
     * A queue of elements currently in the map, ordered by access time. Elements are added to the

          } catch (TimeoutException e) {
            inputs.assertHasDelayed(iFuture, jFuture, e);
          }

          // Finish the two futures in the currently specified order:
          inputs.allFutures.get(iBeforeJ ? i : j).finisher.run();
          inputs.allFutures.get(iBeforeJ ? j : i).finisher.run();

    @ParametricNullness
    public K firstKey() {
      // correctly throws NoSuchElementException when filtered map is empty.
      return keySet().iterator().next();
    }

    @Override
    @ParametricNullness
    public K lastKey() {
      SortedMap<K, V> headMap = sortedMap();
      while (true) {
        // correctly throws NoSuchElementException when filtered map is empty.

          } catch (TimeoutException e) {
            inputs.assertHasDelayed(iFuture, jFuture, e);
          }

          // Finish the two futures in the currently specified order:
          inputs.allFutures.get(iBeforeJ ? i : j).finisher.run();
          inputs.allFutures.get(iBeforeJ ? j : i).finisher.run();

    final AtomicInteger readCount = new AtomicInteger();

    /**
     * A queue of elements currently in the map, ordered by write time. Elements are added to the
     * tail of the queue on write.
     */
    @GuardedBy("this")
    final Queue<ReferenceEntry<K, V>> writeQueue;

    /**
     * A queue of elements currently in the map, ordered by access time. Elements are added to the