* whose next element can always be derived from the previous element. Null elements are not
 * supported, nor is the {@link #remove()} method.
 *
 * <p>Example:
 *
 * <pre>{@code
 * Iterator<Integer> powersOfTwo =
 *     new AbstractSequentialIterator<Integer>(1) {
 *       protected Integer computeNext(Integer previous) {
 *         return (previous == 1 << 30) ? null : previous * 2;
 *       }
 *     };
 * }</pre>
 *

      final C first = first();

      @Override
      @CheckForNull
      protected C computeNext(C previous) {
        return equalsOrThrow(previous, first) ? null : domain.previous(previous);
      }
    };
  }

  private static boolean equalsOrThrow(Comparable<?> left, @CheckForNull Comparable<?> right) {
    return right != null && Range.compareOrThrow(left, right) == 0;
  }

  @Override

      protected @Nullable Integer computeNext(Integer previous) {
        return (previous == last) ? null : previous * 2;
      }
    };
  }

  private static class EmptyAbstractSequentialIterator<T> extends AbstractSequentialIterator<T> {

    public EmptyAbstractSequentialIterator() {
      super(null);
    }

    @Override
    protected T computeNext(T previous) {
      throw new AssertionFailedError();
    }

 * whose next element can always be derived from the previous element. Null elements are not
 * supported, nor is the {@link #remove()} method.
 *
 * <p>Example:
 *
 * <pre>{@code
 * Iterator<Integer> powersOfTwo =
 *     new AbstractSequentialIterator<Integer>(1) {
 *       protected Integer computeNext(Integer previous) {
 *         return (previous == 1 << 30) ? null : previous * 2;
 *       }
 *     };
 * }</pre>
 *

  public void testAdd() {
    ListIterator<String> iterator = create();

    assertTrue(iterator.hasNext());
    assertEquals("a", iterator.next());
    assertEquals("b", iterator.next());
    assertEquals("b", iterator.previous());
    try {
      iterator.add("c");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

  @SuppressWarnings("DoNotCall")
  public void testSet() {

      protected @Nullable Integer computeNext(Integer previous) {
        return (previous == last) ? null : previous * 2;
      }
    };
  }

  private static class EmptyAbstractSequentialIterator<T> extends AbstractSequentialIterator<T> {

    public EmptyAbstractSequentialIterator() {
      super(null);
    }

    @Override
    protected T computeNext(T previous) {
      throw new AssertionFailedError();
    }

  public void testAdd() {
    ListIterator<String> iterator = create();

    assertTrue(iterator.hasNext());
    assertEquals("a", iterator.next());
    assertEquals("b", iterator.next());
    assertEquals("b", iterator.previous());
    try {
      iterator.add("c");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

  @SuppressWarnings("DoNotCall")
  public void testSet() {

But at some point, there was no other option than creating something that provided all these features, taking the best ideas from previous tools, and combining them in the best way possible, using language features that weren't even available before (Python 3.6+ type hints).

</blockquote>

## Investigation

  /** Sets the next entry in the access queue. */
  void setNextInAccessQueue(ReferenceEntry<K, V> next);

  /** Returns the previous entry in the access queue. */
  ReferenceEntry<K, V> getPreviousInAccessQueue();

  /** Sets the previous entry in the access queue. */
  void setPreviousInAccessQueue(ReferenceEntry<K, V> previous);

  /*
   * Implemented by entries that use write order. Write entries are maintained in a doubly-linked

  /** Sets the next entry in the access queue. */
  void setNextInAccessQueue(ReferenceEntry<K, V> next);

  /** Returns the previous entry in the access queue. */
  ReferenceEntry<K, V> getPreviousInAccessQueue();

  /** Sets the previous entry in the access queue. */
  void setPreviousInAccessQueue(ReferenceEntry<K, V> previous);

  /*
   * Implemented by entries that use write order. Write entries are maintained in a doubly-linked