* always true when the iterable has fewer than two elements.
   */
  public static <T extends @Nullable Object> boolean isInOrder(
      Iterable<? extends T> iterable, Comparator<T> comparator) {
    checkNotNull(comparator);
    Iterator<? extends T> it = iterable.iterator();
    if (it.hasNext()) {
      T prev = it.next();
      while (it.hasNext()) {
        T next = it.next();
        if (comparator.compare(prev, next) > 0) {

  private static final Iterable<Integer> ITERABLE_ = Arrays.<Integer>asList();
  private static final Iterable<Integer> ITERABLE_1 = Arrays.asList(1);
  private static final Iterable<Integer> ITERABLE_12 = Arrays.asList(1, 2);
  private static final Iterable<Integer> ITERABLE_123 = Arrays.asList(1, 2, 3);
  private static final Iterable<@Nullable Integer> ITERABLE_NULL = Arrays.asList((Integer) null);

    /**
     * for each構文で使用するために{@link LineIterator}をラップした{@link Iterable}を返します。
     *
     * @param reader
     *            文字列を読み込む{@link Reader}。{@literal null}であってはいけません
     * @return {@link LineIterator}をラップした{@link Iterable}
     */
    public static Iterable<String> iterable(final Reader reader) {
        assertArgumentNotNull("reader", reader);
        return iterable(new BufferedReader(reader));
    }

    /**

    @SuppressWarnings("rawtypes") // the purpose is to test raw type
    Invokable<?, Iterable> delegate =
        Prepender.method("prepend", String.class, Iterable.class).returning(Iterable.class);
    assertEquals(new TypeToken<Iterable<String>>() {}, delegate.getReturnType());
    @SuppressWarnings("unchecked") // prepend() returns Iterable<String>
    Iterable<String> result = delegate.invoke(null, "a", ImmutableList.of("b", "c"));

   *
   * <p><b>Exception:</b> for consistency with separator-based splitters, {@code split("")} does not
   * yield an empty iterable, but an iterable containing {@code ""}. This is the only case in which
   * {@code Iterables.size(split(input))} does not equal {@code IntMath.divide(input.length(),
   * length, CEILING)}. To avoid this behavior, use {@code omitEmptyStrings}.
   *

   *
   * <p><b>Exception:</b> for consistency with separator-based splitters, {@code split("")} does not
   * yield an empty iterable, but an iterable containing {@code ""}. This is the only case in which
   * {@code Iterables.size(split(input))} does not equal {@code IntMath.divide(input.length(),
   * length, CEILING)}. To avoid this behavior, use {@code omitEmptyStrings}.
   *

    @SuppressWarnings("rawtypes") // Iterable.class
    TypeToken<? extends Iterable> genericType = TypeToken.toGenericType(Iterable.class);
    assertEquals(Iterable.class, genericType.getRawType());
    assertEquals(
        Types.newParameterizedType(Iterable.class, Iterable.class.getTypeParameters()[0]),
        genericType.getType());
  }

   *     original iterable.
   * @throws NullPointerException if the specified iterable is null or has any null elements.
   * @since 12.0
   */
  public static <E extends Comparable<? super E>> Collection<List<E>> orderedPermutations(
      Iterable<E> elements) {
    return orderedPermutations(elements, Ordering.natural());
  }

  /**
   * Returns a {@link Collection} of all the permutations of the specified {@link Iterable} using

  }

  private static boolean isEmpty(Iterable<?> iterable) {
    return iterable instanceof Collection
        ? ((Collection<?>) iterable).isEmpty()
        : !iterable.iterator().hasNext();
  }

  public static void assertEmpty(Iterable<?> iterable) {
    if (!isEmpty(iterable)) {
      Assert.fail("Not true that " + iterable + " is empty");
    }
  }

    }

    @Override
    public Iterable<? extends Character> successors(Character node) {
      requestedNodes.add(node);
      return delegate.successors(node);
    }
  }

  private static <N> SuccessorsFunction<N> fixedSuccessors(final Iterable<N> successors) {
    return new SuccessorsFunction<N>() {
      @Override
      public Iterable<N> successors(N n) {
        return successors;