public static <T extends @Nullable Object> Iterable<T> concat(
      Iterable<? extends T> a,
      Iterable<? extends T> b,
      Iterable<? extends T> c,
      Iterable<? extends T> d) {
    return FluentIterable.concat(a, b, c, d);
  }

  /**
   * Combines multiple iterables into a single iterable. The returned iterable has an iterator that

  static final Iterable<Double> INFINITIES =
      Doubles.asList(Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY);
  static final Iterable<Double> FINITE_DOUBLE_CANDIDATES;
  static final Iterable<Double> POSITIVE_FINITE_DOUBLE_CANDIDATES;
  static final Iterable<Double> ALL_DOUBLE_CANDIDATES;
  static final Iterable<Double> DOUBLE_CANDIDATES_EXCEPT_NAN;

  static {

  static final Iterable<Double> INFINITIES =
      Doubles.asList(Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY);
  static final Iterable<Double> FINITE_DOUBLE_CANDIDATES;
  static final Iterable<Double> POSITIVE_FINITE_DOUBLE_CANDIDATES;
  static final Iterable<Double> ALL_DOUBLE_CANDIDATES;
  static final Iterable<Double> DOUBLE_CANDIDATES_EXCEPT_NAN;

  static {

  }

  private void testGetOnAbc(Iterable<String> iterable) {
    try {
      Iterables.get(iterable, -1);
      fail();
    } catch (IndexOutOfBoundsException expected) {
    }
    assertEquals("a", Iterables.get(iterable, 0));
    assertEquals("b", Iterables.get(iterable, 1));
    assertEquals("c", Iterables.get(iterable, 2));
    try {
      Iterables.get(iterable, 3);
      fail();

    public Iterable<UseIterable<? extends Iterable<?>>>
        wildcardOfImplicitBoundedIsSubtypeOfWildcardOfExplicitlyBounded(
            List<UseIterable<?>> withImplicitBounds) {
      return isSubtype(withImplicitBounds);
    }

    @TestSubtype(suppressGetSupertype = true, suppressGetSubtype = true)
    public Iterable<UseSerializableIterable<? extends Iterable<?>>>

    Iterable<String> set = newHashSet("a", "b");
    assertFalse(FluentIterable.from(set).contains("c"));
  }

  public void testContains_nonNullIterableYes() {
    Iterable<String> set = iterable("a", null, "b");
    assertTrue(FluentIterable.from(set).contains("b"));
  }

  public void testContains_nonNullIterableNo() {
    Iterable<String> iterable = iterable("a", "b");
    assertFalse(FluentIterable.from(iterable).contains("c"));

  // Ordering<Iterable<String>> o =
  //     Ordering.<String>natural().lexicographical();
  public <S extends T> Ordering<Iterable<S>> lexicographical() {
    /*
     * Note that technically the returned ordering should be capable of
     * handling not just {@code Iterable<S>} instances, but also any {@code
     * Iterable<? extends S>}. However, the need for this comes up so rarely

   *     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

   * already a {@code FluentIterable}.
   *
   * <p><b>{@code Stream} equivalent:</b> {@code iterable.stream()} if {@code iterable} is a {@link
   * Collection}; {@code StreamSupport.stream(iterable.spliterator(), false)} otherwise.
   */
  public static <E extends @Nullable Object> FluentIterable<E> from(final Iterable<E> iterable) {
    return (iterable instanceof FluentIterable)

    Iterable<Double> iterable = iterable(Collections.<Double>emptySet());
    assertThat(ImmutableDoubleArray.copyOf(iterable)).isSameInstanceAs(ImmutableDoubleArray.of());
  }

  public void testCopyOf_iterable_notCollection_nonempty() {
    List<Double> list = Arrays.asList(0.0, 1.0, 3.0);
    ImmutableDoubleArray iia = ImmutableDoubleArray.copyOf(iterable(list));
    list.set(2, 2.0);