* both use cases by using @PolyNull. (By contrast, we can't use @PolyNull for our superinterface
   * (`implements Function<@PolyNull A, @PolyNull B>`), at least as far as I know.)
   */
  public Iterable<B> convertAll(Iterable<? extends A> fromIterable) {
    checkNotNull(fromIterable, "fromIterable");
    return () ->
        new Iterator<B>() {
          private final Iterator<? extends A> fromIterator = fromIterable.iterator();

   * wish to override {@link #addAll(int, Collection)} to forward to this implementation.
   *
   * @since 7.0
   */
  protected boolean standardAddAll(int index, Iterable<? extends E> elements) {
    return Lists.addAllImpl(this, index, elements);
  }

  /**
   * A sensible default implementation of {@link #indexOf}, in terms of {@link #listIterator()}. If

 *
 * <p>The edge is a self-loop if, and only if, the two endpoints are equal.
 *
 * @author James Sexton
 * @since 20.0
 */
@Beta
@Immutable(containerOf = {"N"})
public abstract class EndpointPair<N> implements Iterable<N> {
  private final N nodeU;
  private final N nodeV;

  private EndpointPair(N nodeU, N nodeV) {
    this.nodeU = checkNotNull(nodeU);
    this.nodeV = checkNotNull(nodeV);
  }

                new TestStringSetGenerator() {
                  @Override
                  protected Set<String> create(String[] elements) {
                    Iterable<String> rowKeys = ImmutableSet.copyOf(elements);
                    Iterable<Integer> columnKeys = ImmutableList.of(1, 2, 3);
                    Table<String, Integer, Character> table =
                        ArrayTable.create(rowKeys, columnKeys);

    @SuppressWarnings("unchecked")
    @Override
    public Entry<Country, String>[] createArray(int length) {
      return (Entry<Country, String>[]) new Entry<?, ?>[length];
    }

    @Override
    public Iterable<Entry<Country, String>> order(List<Entry<Country, String>> insertionOrder) {
      return insertionOrder;
    }

    @Override
    public Country[] createKeyArray(int length) {
      return new Country[length];

  }

  @MapFeature.Require(SUPPORTS_PUT)
  public void testPutAll_nullCollectionReference() {
    assertThrows(NullPointerException.class, () -> getMap().putAll(null));
  }

  private void putAll(Iterable<Entry<K, V>> entries) {
    Map<K, V> map = new LinkedHashMap<>();
    for (Entry<K, V> entry : entries) {
      map.put(entry.getKey(), entry.getValue());
    }
    getMap().putAll(map);
  }

  /**

 *
 * {@snippet :
 * class MySubtypeTests extends SubtypeTester {
 *   @TestSubtype(suppressGetSubtype = true, suppressGetSupertype = true)
 *   public <T> Iterable<? extends T> listIsSubtypeOfIterable(List<T> list) {
 *     return isSubtype(list);
 *   }
 *
 *   @TestSubtype
 *   public List<String> intListIsNotSubtypeOfStringList(List<Integer> intList) {

    assertTrue(emptyConcat.isEmpty());
  }

  public void testConcat_infiniteIterable() throws IOException {
    CharSource source = CharSource.wrap("abcd");
    Iterable<CharSource> cycle = Iterables.cycle(ImmutableList.of(source));
    CharSource concatenated = CharSource.concat(cycle);

    String expected = "abcdabcd";

   * throws a {@link NullPointerException}.
   *
   * <p>To find the first non-null element in an iterable, use {@code Iterables.find(iterable,
   * Predicates.notNull())}. For varargs, use {@code Iterables.find(Arrays.asList(a, b, c, ...),
   * Predicates.notNull())}, static importing as necessary.
   *

 *
 * <h4>Combining</h4>
 *
 * To derive a {@code ClosingFuture} from two or more input steps, pass the input steps to {@link
 * #whenAllComplete(Iterable)} or {@link #whenAllSucceed(Iterable)} or its overloads.
 *
 * <h3>Cancelling</h3>
 *
 * Any step in a pipeline can be {@linkplain #cancel(boolean) cancelled}, even after another step