* null} if they were already garbage collected.
   *
   * @since 19.0
   */
  public static <K, V> RemovalNotification<K, V> create(
      @CheckForNull K key, @CheckForNull V value, RemovalCause cause) {
    return new RemovalNotification<>(key, value, cause);
  }

  private RemovalNotification(@CheckForNull K key, @CheckForNull V value, RemovalCause cause) {
    super(key, value);
    this.cause = checkNotNull(cause);
  }

            .maximumSize(0)
            .removalListener(listener)
            .build(constantLoader(computed));

    Object key = new Object();
    assertSame(computed, cache.getUnchecked(key));
    RemovalNotification<Object, Object> notification = listener.remove();
    assertSame(key, notification.getKey());
    assertSame(computed, notification.getValue());
    assertSame(RemovalCause.SIZE, notification.getCause());

            .maximumSize(0)
            .removalListener(listener)
            .build(constantLoader(computed));

    Object key = new Object();
    assertSame(computed, cache.getUnchecked(key));
    RemovalNotification<Object, Object> notification = listener.remove();
    assertSame(key, notification.getKey());
    assertSame(computed, notification.getValue());
    assertSame(RemovalCause.SIZE, notification.getCause());

    // contain the computed value (b -> b), since the clear() happened before the computation
    // completed.
    assertEquals(1, listener.size());
    RemovalNotification<String, String> notification = listener.remove();
    assertEquals("a", notification.getKey());
    assertEquals("a", notification.getValue());
    assertEquals(1, cache.size());

  }

  public void testComputeIfAbsent_removalListener() {
    List<RemovalNotification<Object, Object>> notifications = new ArrayList<>();
    RemovalListener<Object, Object> removalListener =
        new RemovalListener<Object, Object>() {
          @Override
          public void onRemoval(RemovalNotification<Object, Object> notification) {
            notifications.add(notification);
          }
        };

  private long currentTimeNanos() {
    return ticker.read();
  }

  private void alertListenerIfPresent(K key, V value, RemovalCause cause) {
    if (removalListener != null) {
      removalListener.onRemoval(RemovalNotification.create(key, value, cause));
    }
  }

  @SuppressWarnings("GoodTime") // timestamps as numeric primitives
  private V load(K key) throws ExecutionException {
    long startTime = ticker.read();

    final RuntimeException e = new RuntimeException();
    RemovalListener<Object, Object> listener =
        new RemovalListener<Object, Object>() {
          @Override
          public void onRemoval(RemovalNotification<Object, Object> notification) {
            throw e;
          }
        };

    CacheBuilder<Object, Object> builder = createCacheBuilder().removalListener(listener);

    final int[] stats = new int[4];

    RemovalListener<Integer, Integer> countingListener =
        new RemovalListener<Integer, Integer>() {
          @Override
          public void onRemoval(RemovalNotification<Integer, Integer> notification) {
            switch (notification.getCause()) {
              case EXPIRED:
                stats[0]++;
                break;
              case EXPLICIT:

      totalWeight -= weight;
      if (cause.wasEvicted()) {
        statsCounter.recordEviction();
      }
      if (map.removalNotificationQueue != DISCARDING_QUEUE) {
        RemovalNotification<K, V> notification = RemovalNotification.create(key, value, cause);
        map.removalNotificationQueue.offer(notification);
      }
    }

    /**

          return new SimpleStatsCounter();
        }
      };

  enum NullListener implements RemovalListener<Object, Object> {
    INSTANCE;

    @Override
    public void onRemoval(RemovalNotification<Object, Object> notification) {}
  }

  enum OneWeigher implements Weigher<Object, Object> {
    INSTANCE;

    @Override
    public int weigh(Object key, Object value) {
      return 1;
    }