* returned by {@code get(rowKeyList().get(rowIndex), columnKeyList().get(columnIndex))}, but this
   * method runs more quickly.
   *
   * @param rowIndex position of the row key in {@link #rowKeyList()}
   * @param columnIndex position of the row key in {@link #columnKeyList()}
   * @return the value with the specified row and column

      testConstructorParameter(ctor, nullIndex);
    }
  }

  /**
   * Verifies that {@code method} produces a {@link NullPointerException} or {@link
   * UnsupportedOperationException} when the parameter in position {@code paramIndex} is null. If
   * this parameter is marked nullable, this method does nothing.
   *
   * @param instance the instance to invoke {@code method} on, or null if {@code method} is static
   */

  abstract ImmutableSortedSet<E> createDescendingSet();

  /** @since 12.0 */
  @GwtIncompatible // NavigableSet
  @Override
  public abstract UnmodifiableIterator<E> descendingIterator();

  /** Returns the position of an element within the set, or -1 if not present. */
  abstract int indexOf(@CheckForNull Object target);

  /*
   * This class is used to serialize all ImmutableSortedSet instances,

    return (++i == items.length) ? 0 : i;
  }

  /**
   * Inserts element at current put position, advances, and signals. Call only when occupying
   * monitor.
   */
  private void insert(E x) {
    items[putIndex] = x;
    putIndex = inc(putIndex);
    ++count;
  }

  /**
   * Extracts element at current take position, advances, and signals. Call only when occupying
   * monitor.
   */
  private E extract() {

    doTestSet(e3());
  }

  private void doTestSet(E newValue) {
    int index = aValidIndex();
    E initialValue = getList().get(index);
    assertEquals(
        "set(i, x) should return the old element at position i.",
        initialValue,
        getList().set(index, newValue));
    assertEquals("After set(i, x), get(i) should return x", newValue, getList().get(index));

      stackWithLastReturnedElementAtTop.pop();
      stackWithLastReturnedElementAtTop.push(e);
    }

    /**
     * Moves the given element from its current position in {@link #nextElements} to the top of the
     * stack so that it is returned by the next call to {@link Iterator#next()}. If the element is
     * not in {@link #nextElements}, this method throws an {@link UnknownElementException}.

    return indexIn(sequence, 0);
  }

  /**
   * Returns the index of the first matching BMP character in a character sequence, starting from a
   * given position, or {@code -1} if no character matches after that position.
   *
   * <p>The default implementation iterates over the sequence in forward order, beginning at {@code
   * start}, calling {@link #matches} for each character.
   *

    for (int i = start; i < end; i++) {
      if (array[i] == target) {
        return i;
      }
    }
    return -1;
  }

  /**
   * Returns the start position of the first occurrence of the specified {@code target} within
   * {@code array}, or {@code -1} if there is no such occurrence.
   *

    return (++i == items.length) ? 0 : i;
  }

  /**
   * Inserts element at current put position, advances, and signals. Call only when occupying
   * monitor.
   */
  private void insert(E x) {
    items[putIndex] = x;
    putIndex = inc(putIndex);
    ++count;
  }

  /**
   * Extracts element at current take position, advances, and signals. Call only when occupying
   * monitor.
   */
  private E extract() {

        return Iterators.forArray(1, 2, 3);
      }
    }.test();
  }

  /*
   * TODO(cpovirk): Test forArray with ListIteratorTester (not just IteratorTester), including with
   * a start position other than 0.
   */

  public void testForEnumerationEmpty() {
    Enumeration<Integer> enumer = enumerate();
    Iterator<Integer> iter = Iterators.forEnumeration(enumer);