void executeAndCompare(ListIterator<E> reference, Iterator<E> target) {
          internalExecuteAndCompare(reference, target, NEXT_METHOD);
        }
      };
  Stimulus<E, Iterator<E>> remove =
      new Stimulus<E, Iterator<E>>("remove") {
        @Override
        void executeAndCompare(ListIterator<E> reference, Iterator<E> target) {
          internalExecuteAndCompare(reference, target, REMOVE_METHOD);
        }
      };

    if (reference == null) {
      throw new NullPointerException();
    }
    return reference;
  }

  /**
   * Ensures that an object reference passed as a parameter to the calling method is not null.
   *
   * @param reference an object reference
   * @param errorMessage the exception message to use if the check fails; will be converted to a

        map.put(keyOne, valueOne);
        InternalEntry<Object, Object, ?> entry = segment.getEntry(keyOne, hashOne);

        @SuppressWarnings("unchecked")
        Reference<Object> reference = (Reference<Object>) entry;
        reference.enqueue();

        map.put(keyTwo, valueTwo);
        assertFalse(map.containsKey(keyOne));
        assertFalse(map.containsValue(valueOne));
        assertNull(map.get(keyOne));

        map.put(keyOne, valueOne);
        InternalEntry<Object, Object, ?> entry = segment.getEntry(keyOne, hashOne);

        @SuppressWarnings("unchecked")
        Reference<Object> reference = (Reference<Object>) entry;
        reference.enqueue();

        map.put(keyTwo, valueTwo);
        assertFalse(map.containsKey(keyOne));
        assertFalse(map.containsValue(valueOne));
        assertNull(map.get(keyOne));

        void executeAndCompare(ListIterator<E> reference, Iterator<E> target) {
          internalExecuteAndCompare(reference, target, NEXT_METHOD);
        }
      };
  Stimulus<E, Iterator<E>> remove =
      new Stimulus<E, Iterator<E>>("remove") {
        @Override
        void executeAndCompare(ListIterator<E> reference, Iterator<E> target) {
          internalExecuteAndCompare(reference, target, REMOVE_METHOD);
        }
      };

    TreeMultiset<E> multiset = create();
    Iterables.addAll(multiset, elements);
    return multiset;
  }

  private final transient Reference<AvlNode<E>> rootReference;
  private final transient GeneralRange<E> range;
  private final transient AvlNode<E> header;

  TreeMultiset(Reference<AvlNode<E>> rootReference, GeneralRange<E> range, AvlNode<E> endLink) {
    super(range.comparator());
    this.rootReference = rootReference;

/**
 * An immutable object that may contain a non-null reference to another object. Each instance of
 * this type either contains a non-null reference, or contains nothing (in which case we say that
 * the reference is "absent"); it is never said to "contain {@code null}".
 *
 * <p>A non-null {@code Optional<T>} reference can be used as a replacement for a nullable {@code T}

        .isFalse();
    assertEquals(1, Booleans.asList(ARRAY_FALSE_TRUE).lastIndexOf(true));
    List<Boolean> reference = Booleans.asList(ARRAY_FALSE);
    assertEquals(Booleans.asList(ARRAY_FALSE), reference);
    // Explicitly call `equals`; `assertEquals` might return fast
    assertThat(reference.equals(reference)).isTrue();
  }

  public void testAsListHashcode() {
    assertThat(Booleans.asList(EMPTY).hashCode()).isEqualTo(1);

        .isFalse();
    assertEquals(1, Booleans.asList(ARRAY_FALSE_TRUE).lastIndexOf(true));
    List<Boolean> reference = Booleans.asList(ARRAY_FALSE);
    assertEquals(Booleans.asList(ARRAY_FALSE), reference);
    // Explicitly call `equals`; `assertEquals` might return fast
    assertThat(reference.equals(reference)).isTrue();
  }

  public void testAsListHashcode() {
    assertThat(Booleans.asList(EMPTY).hashCode()).isEqualTo(1);

     * been cleared by this point.
     */
    reference.clear();

    if (reference == frqReference) {
      /*
       * The client no longer has a reference to the FinalizableReferenceQueue. We can stop.
       */
      return false;
    }

    try {
      finalizeReferentMethod.invoke(reference);
    } catch (Throwable t) {