* href="http://gee.cs.oswego.edu/dl/html/StreamParallelGuidance.html">efficiently splittable</a>.
   * This may harm parallel performance.
   */
  @Beta
  public static <A extends @Nullable Object, B extends @Nullable Object, R extends @Nullable Object>
      Stream<R> zip(
          Stream<A> streamA, Stream<B> streamB, BiFunction<? super A, ? super B, R> function) {
    checkNotNull(streamA);
    checkNotNull(streamB);

@ElementTypesAreNonnullByDefault
class CompactLinkedHashMap<K extends @Nullable Object, V extends @Nullable Object>
    extends CompactHashMap<K, V> {
  // TODO(lowasser): implement removeEldestEntry so this can be used as a drop-in replacement

  /** Creates an empty {@code CompactLinkedHashMap} instance. */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      CompactLinkedHashMap<K, V> create() {

import junit.framework.Assert;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A test utility that verifies that your methods and constructors throw {@link
 * NullPointerException} or {@link UnsupportedOperationException} whenever null is passed to a
 * parameter whose declaration or type isn't annotated with an annotation with the simple name
 * {@code Nullable}, {@code CheckForNull}, {@code NullableType}, or {@code NullableDecl}.
 *

  private static final Iterable<@Nullable Integer> ITERABLE_NULL = Arrays.asList((Integer) null);
  private static final Iterable<@Nullable Integer> ITERABLE_NULL_NULL =
      Arrays.asList((Integer) null, null);
  private static final Iterable<@Nullable Integer> ITERABLE_NULL_1 = Arrays.asList(null, 1);
  private static final Iterable<@Nullable Integer> ITERABLE_1_NULL = Arrays.asList(1, null);

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * An iterator that transforms a backing list iterator; for internal use. This avoids the object
 * overhead of constructing a {@link Function} for internal methods.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class TransformedListIterator<F extends @Nullable Object, T extends @Nullable Object>

 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class AbstractSortedKeySortedSetMultimap<
        K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractSortedSetMultimap<K, V> {

  AbstractSortedKeySortedSetMultimap(SortedMap<K, Collection<V>> map) {
    super(map);
  }

  @Override

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * An iterator that transforms a backing list iterator; for internal use. This avoids the object
 * overhead of constructing a {@link Function} for internal methods.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class TransformedListIterator<F extends @Nullable Object, T extends @Nullable Object>

public final class MutableClassToInstanceMap<B extends @Nullable Object>
    extends ForwardingMap<Class<? extends @NonNull B>, B>
    implements ClassToInstanceMap<B>, Serializable {

  /**
   * Returns a new {@code MutableClassToInstanceMap} instance backed by a {@link HashMap} using the
   * default initial capacity and load factor.
   */
  public static <B extends @Nullable Object> MutableClassToInstanceMap<B> create() {

  private static final class AlwaysEqual extends Ordering<@Nullable Object>
      implements Serializable {
    private static final AlwaysEqual INSTANCE = new AlwaysEqual();

    @Override
    @SuppressWarnings("UnusedVariable") // intentionally weird Comparator
    public int compare(@Nullable Object o1, @Nullable Object o2) {
      return 0;
    }

    @Override

  public void testCopyOfNullKey() {
    ArrayListMultimap<@Nullable String, Integer> input = ArrayListMultimap.create();
    input.put(null, 1);
    assertThrows(
        NullPointerException.class,
        () -> ImmutableListMultimap.copyOf((ArrayListMultimap<String, Integer>) input));
  }

  public void testCopyOfNullValue() {
    ArrayListMultimap<String, @Nullable Integer> input = ArrayListMultimap.create();