/**
     * Returns true if this reference contains an active value, meaning one that is still considered
     * present in the cache. Active values consist of live values, which are returned by cache
     * lookups, and dead values, which have been evicted but awaiting removal. Non-active values
     * consist strictly of loading values, though during refresh a value may be both active and
     * loading.
     */
    boolean isActive();

    // no notification sent with removeLoadingValue
    assertTrue(map.removalNotificationQueue.isEmpty());
    assertEquals(0, segment.count);
    assertNull(table.get(0));

    // active
    Object value = new Object();
    DummyValueReference<Object, Object> previousRef = DummyValueReference.create(value);
    valueRef = new LoadingValueReference<>(previousRef);
    entry.setValueReference(valueRef);

    // no notification sent with removeLoadingValue
    assertTrue(map.removalNotificationQueue.isEmpty());
    assertEquals(0, segment.count);
    assertNull(table.get(0));

    // active
    Object value = new Object();
    DummyValueReference<Object, Object> previousRef = DummyValueReference.create(value);
    valueRef = new LoadingValueReference<>(previousRef);
    entry.setValueReference(valueRef);

    /**
     * Returns true if this reference contains an active value, meaning one that is still considered
     * present in the cache. Active values consist of live values, which are returned by cache
     * lookups, and dead values, which have been evicted but awaiting removal. Non-active values
     * consist strictly of loading values, though during refresh a value may be both active and
     * loading.
     */
    boolean isActive();

   * backing set. The returned map does not support put operations.
   *
   * <p><b>Warning:</b> If the function rejects {@code null}, caution is required to make sure the
   * set does not contain {@code null}, because the view cannot stop {@code null} from being added
   * to the set.
   *