* iterator supports it.
   *
   * <p><b>Java 8+ users:</b> The {@code Stream} equivalent of this method is {@code
   * Stream.concat(a, b)}.
   */
  public static <T extends @Nullable Object> Iterable<T> concat(
      Iterable<? extends T> a, Iterable<? extends T> b) {
    return FluentIterable.concat(a, b);
  }

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

      } catch (IllegalStateException expected) {
      }
    }
  }

  public void testIsValid() {
    final Iterable<String> validCases = Iterables.concat(VALID_NAME, PS, NO_PS, NON_PS);
    final Iterable<String> invalidCases =
        Iterables.concat(INVALID_NAME, VALID_IP_ADDRS, INVALID_IP_ADDRS);

    for (String valid : validCases) {
      assertTrue(valid, InternetDomainName.isValid(valid));
    }

   * returns an {@code ImmutableRangeSet}.
   *
   * @since 21.0
   */
  public ImmutableRangeSet<C> union(RangeSet<C> other) {
    return unionOf(Iterables.concat(asRanges(), other.asRanges()));
  }

  /**
   * Returns a new range set consisting of the intersection of this range set and {@code other}.
   *
   * <p>This is essentially the same as {@code

   * returns an {@code ImmutableRangeSet}.
   *
   * @since 21.0
   */
  public ImmutableRangeSet<C> union(RangeSet<C> other) {
    return unionOf(Iterables.concat(asRanges(), other.asRanges()));
  }

  /**
   * Returns a new range set consisting of the intersection of this range set and {@code other}.
   *
   * <p>This is essentially the same as {@code

    Stream<String> concatenated =
        Streams.concat(Stream.of("a"), streamB, Stream.empty(), Stream.of("c", "d"));
    assertThat(concatenated).containsExactly("a", "b", "c", "d").inOrder();
    concatenated.close();
    assertThat(closeCountB.get()).isEqualTo(1);
  }

  public void testConcat_refStream_closeIsPropagated_Stream_concat() {
    // Just to demonstrate behavior of Stream::concat in the standard library

      }

      @Override
      public boolean cancel(boolean mayInterruptIfRunning) {
        boolean cancelled = super.cancel(mayInterruptIfRunning);
        if (cancelled) {
          // Unless it is cancelled, the delegate may continue being scheduled
          scheduledDelegate.cancel(mayInterruptIfRunning);

          // TODO(user): Cancel "this" if "scheduledDelegate" is cancelled.
        }

      } catch (IllegalStateException expected) {
      }
    }
  }

  public void testIsValid() {
    final Iterable<String> validCases = Iterables.concat(VALID_NAME, PS, NO_PS, NON_PS);
    final Iterable<String> invalidCases =
        Iterables.concat(INVALID_NAME, VALID_IP_ADDRS, INVALID_IP_ADDRS);

    for (String valid : validCases) {
      assertTrue(valid, InternetDomainName.isValid(valid));
    }

    Iterable<Integer> result = Iterables.concat(list1, list2, list3, list4, list5);
    assertEquals(asList(1, 4, 7, 8, 9, 10), newArrayList(result));
    assertEquals("[1, 4, 7, 8, 9, 10]", result.toString());
  }

  public void testConcatNullPointerException() {
    List<Integer> list1 = newArrayList(1);
    List<Integer> list2 = newArrayList(4);

    try {
      Iterables.concat(list1, null, list2);
      fail();

    Iterable<Integer> result = Iterables.concat(list1, list2, list3, list4, list5);
    assertEquals(asList(1, 4, 7, 8, 9, 10), newArrayList(result));
    assertEquals("[1, 4, 7, 8, 9, 10]", result.toString());
  }

  public void testConcatNullPointerException() {
    List<Integer> list1 = newArrayList(1);
    List<Integer> list2 = newArrayList(4);

    try {
      Iterables.concat(list1, null, list2);
      fail();