assertSame(valueThree, newFirst.getValue());
    assertEquals(hashThree, newFirst.getHash());
    assertNull(newFirst.getNext());
  }

  @SuppressWarnings("GuardedBy")
  public void testExpand_cleanup() {
    MapMakerInternalMap<Object, Object, ?, ?> map =
        makeMap(createMapMaker().concurrencyLevel(1).initialCapacity(1));
    Segment<Object, Object, ?, ?> segment = map.segments[0];

    assertSame(valueThree, newFirst.getValue());
    assertEquals(hashThree, newFirst.getHash());
    assertNull(newFirst.getNext());
  }

  @SuppressWarnings("GuardedBy")
  public void testExpand_cleanup() {
    MapMakerInternalMap<Object, Object, ?, ?> map =
        makeMap(createMapMaker().concurrencyLevel(1).initialCapacity(1));
    Segment<Object, Object, ?, ?> segment = map.segments[0];

 * </ul>
 *
 * <p>Invalid:
 *
 * <ul>
 *   <li>Expired: time expired (key/value may still be set)
 *   <li>Collected: key/value was partially collected, but not yet cleaned up
 *   <li>Unset: marked as unset, awaiting cleanup or reuse
 * </ul>
 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault
interface ReferenceEntry<K, V> {
  /** Returns the value reference from this entry. */
  @CheckForNull

 * #putAll} is implemented in terms of {@link #put}, {@link #invalidateAll(Iterable)} is implemented
 * in terms of {@link #invalidate}. The method {@link #cleanUp} is a no-op. All other methods throw
 * an {@link UnsupportedOperationException}.
 *
 * @author Charles Fry
 * @since 11.0
 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault

 * #putAll} is implemented in terms of {@link #put}, {@link #invalidateAll(Iterable)} is implemented
 * in terms of {@link #invalidate}. The method {@link #cleanUp} is a no-op. All other methods throw
 * an {@link UnsupportedOperationException}.
 *
 * @author Charles Fry
 * @since 11.0
 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault

   * @param queue that should finalize the referent
   */
  protected FinalizableWeakReference(@CheckForNull T referent, FinalizableReferenceQueue queue) {
    super(referent, queue.queue);
    queue.cleanUp();
  }

  @SuppressWarnings("InfiniteLoopStatement")
  @Override
  public void run() {
    while (true) {
      try {
        if (!cleanUp(queue.remove())) {
          break;
        }
      } catch (InterruptedException e) {
        // ignore
      }
    }
  }

  /**
   * Cleans up the given reference and any other references already in the queue. Catches and logs
   * all throwables.
   *

 * implemented in terms of {@link #getIfPresent}; {@link #putAll} is implemented in terms of {@link
 * #put}, {@link #invalidateAll(Iterable)} is implemented in terms of {@link #invalidate}. The
 * method {@link #cleanUp} is a no-op. All other methods throw an {@link
 * UnsupportedOperationException}.
 *
 * @author Charles Fry
 * @since 10.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

        tryDrainReferenceQueues();
        return null;
      }

      return value;
    }

    /**
     * Performs routine cleanup following a read. Normally cleanup happens during writes, or from
     * the cleanupExecutor. If cleanup is not observed after a sufficient number of reads, try
     * cleaning up from the read thread.
     */
    void postReadCleanup() {

  ConcurrentMap<K, V> asMap();

  /**
   * Performs any pending maintenance operations needed by the cache. Exactly which activities are
   * performed -- if any -- is implementation-dependent.
   */
  void cleanUp();