*/
        public Entry getPrevious() {
            if (previous != SLinkedList.this.header) {
                return previous;
            }
            return null;
        }

        /**
         * 要素を削除します。
         */
        public void remove() {
            previous.next = next;
            next.previous = previous;
            --size;
        }

        /**

      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();
    }

      switch (boundType) {
        case CLOSED:
          return this;
        case OPEN:
          C previous = domain.previous(endpoint);
          return (previous == null) ? Cut.<C>belowAll() : new AboveValue<C>(previous);
        default:
          throw new AssertionError();
      }
    }

    @Override

  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() {

   *     minValue()}
   */
  @CheckForNull
  public abstract C previous(C value);

  /**
   * Returns a signed value indicating how many nested invocations of {@link #next} (if positive) or
   * {@link #previous} (if negative) are needed to reach {@code end} starting from {@code start}.

      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

      switch (boundType) {
        case CLOSED:
          return this;
        case OPEN:
          C previous = domain.previous(endpoint);
          return (previous == null) ? Cut.<C>belowAll() : new AboveValue<C>(previous);
        default:
          throw new AssertionError();
      }
    }

    @Override