*/
    protected abstract List<Double> create(Double[] elements);

    @Override
    public Double[] createArray(int length) {
      return new Double[length];
    }

    /** Returns the original element list, unchanged. */
    @Override
    public List<Double> order(List<Double> insertionOrder) {
      return insertionOrder;
    }
  }

  @J2ktIncompatible
  @GwtIncompatible // used only from suite

     */
    protected abstract List<Long> create(Long[] elements);

    @Override
    public Long[] createArray(int length) {
      return new Long[length];
    }

    /** Returns the original element list, unchanged. */
    @Override
    public List<Long> order(List<Long> insertionOrder) {
      return insertionOrder;
    }
  }

  @J2ktIncompatible
  @GwtIncompatible // used only from suite

 *
 * <p>If neither {@link #skipNulls()} nor {@link #useForNull(String)} is specified, the joining
 * methods will throw {@link NullPointerException} if any given element is null.
 *
 * <p><b>Warning: joiner instances are always immutable</b>; a configuration method such as {@code
 * useForNull} has no effect on the instance it is invoked on! You must store and use the new joiner

   * @return an {@code Object} that is a {@code byte[]}, {@code short[]}, or {@code int[]}, the
   *     smallest possible to fit {@code tableSize}; or an {@code Object[]} where [0] is one of
   *     these; [1] indicates how many element pairs in {@code alternatingKeysAndValues} are valid;
   *     and [2] is a {@link Builder.DuplicateKey} for the first duplicate key encountered.
   */
  @CheckForNull
  private static Object createHashTable(

    return CollectCollectors.toImmutableSetMultimap(keyFunction, valueFunction);
  }

  /**
   * Returns a {@code Collector} accumulating entries into an {@code ImmutableSetMultimap}. Each
   * input element is mapped to a key and a stream of values, each of which are put into the
   * resulting {@code Multimap}, in the encounter order of the stream and the encounter order of the
   * streams of values.
   *
   * <p>Example:

    this(multimap.keySet().size());
    putAll(multimap);
  }

  /**
   * Adds a new node for the specified key-value pair before the specified {@code nextSibling}
   * element, or at the end of the list if {@code nextSibling} is null. Note: if {@code nextSibling}
   * is specified, it MUST be for a node for the same {@code key}!
   */
  @CanIgnoreReturnValue
  private Node<K, V> addNode(

      assertNull(q.poll(0, MILLISECONDS));
      assertEquals("[]", q.toString());
      assertTrue(Arrays.equals(q.toArray(), new Object[0]));
      assertFalse(q.iterator().hasNext());
      try {
        q.element();
        shouldThrow();
      } catch (NoSuchElementException success) {
      }
      try {
        q.iterator().next();
        shouldThrow();
      } catch (NoSuchElementException success) {

      @Override
      public Iterable<? extends Character> successors(Character node) {
        checkArgument(
            graphMap.containsKey(node) || graphMap.containsValue(node),
            "Node %s is not an element of this graph",
            node);
        return Ordering.natural().immutableSortedCopy(graphMap.get(node));
      }
    };
  }

  private static ImmutableGraph<Character> createSingleRootGraph() {

  // Query Operations

  /**
   * Returns the number of occurrences of {@code element} in this multiset.
   *
   * @param element the element to look for
   * @return the nonnegative number of occurrences of the element
   */
  @Override
  public int count(@CheckForNull Object element) {
    AtomicInteger existingCounter = Maps.safeGet(countMap, element);
    return (existingCounter == null) ? 0 : existingCounter.get();
  }

    /**
     * Return the index of the next lower element in the list, or {@code -1} if there is no such
     * element.
     */
    NEXT_LOWER {
      @Override
      int resultIndex(int higherIndex) {
        return higherIndex - 1;
      }
    },
    /**
     * Return the index of the next higher element in the list, or {@code list.size()} if there is
     * no such element.
     */
    NEXT_HIGHER {