*/
    <T> boolean replace(@Nonnull Key<T> key, @Nullable T oldValue, @Nullable T newValue);

    /**
     * Gets the session data associated with the specified key.
     *
     * @param key the key for which to retrieve the session data, must not be {@code null}
     * @return the session data associated with the key or {@code null} if none
     */
    @Nullable
    <T> T get(@Nonnull Key<T> key);

    /**

import com.google.common.collect.ListMultimap;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A generator for {@code ListMultimap} implementations based on test data.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface TestListMultimapGenerator<K extends @Nullable Object, V extends @Nullable Object>

  "nullness", // TODO(b/147136275): Remove once our checker understands & and |.
})
abstract class AbstractCatchingFuture<
        V extends @Nullable Object, X extends Throwable, F, T extends @Nullable Object>
    extends FluentFuture.TrustedFuture<V> implements Runnable {
  static <V extends @Nullable Object, X extends Throwable> ListenableFuture<V> create(
      ListenableFuture<? extends V> input,
      Class<X> exceptionType,

import java.util.List;
import java.util.Map.Entry;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A container class for the five sample elements we need for testing.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public class SampleElements<E extends @Nullable Object> implements Iterable<E> {
  // TODO: rename e3, e4 => missing1, missing2
  private final E e0;

@SuppressWarnings("JUnit4ClassUsedInJUnit3")
@ElementTypesAreNonnullByDefault
public class SortedSetNavigationTester<E extends @Nullable Object> extends AbstractSetTester<E> {

  private SortedSet<E> sortedSet;
  private List<E> values;
  private @Nullable E a;
  private @Nullable E b;
  private @Nullable E c;

  @Override
  public void setUp() throws Exception {
    super.setUp();
    sortedSet = (SortedSet<E>) getSet();

@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
public final class LinkedHashMultiset<E extends @Nullable Object>
    extends AbstractMapBasedMultiset<E> {

  /** Creates a new, empty {@code LinkedHashMultiset} using the default initial capacity. */
  public static <E extends @Nullable Object> LinkedHashMultiset<E> create() {
    return create(ObjectCountHashMap.DEFAULT_SIZE);
  }

  /**

import org.apache.maven.api.annotations.Nullable;

import static org.apache.maven.api.services.BaseRequest.nonNull;

/**
 *
 * @since 4.0.0
 */
@Experimental
public interface VersionRangeResolverRequest {

    @Nonnull
    Session getSession();

    @Nonnull
    ArtifactCoordinates getArtifactCoordinates();

    @Nullable
    List<RemoteRepository> getRepositories();

    @Nonnull

import org.apache.maven.api.annotations.Nullable;

import static org.apache.maven.api.services.BaseRequest.nonNull;

/**
 *
 * @since 4.0.0
 */
@Experimental
public interface VersionResolverRequest {

    @Nonnull
    Session getSession();

    @Nonnull
    ArtifactCoordinates getArtifactCoordinates();

    @Nullable
    List<RemoteRepository> getRepositories();

    @Nonnull

 * @author Louis Wasserman
 */
@GwtIncompatible // not worth using in GWT for now
@ElementTypesAreNonnullByDefault
class CompactLinkedHashSet<E extends @Nullable Object> extends CompactHashSet<E> {

  /** Creates an empty {@code CompactLinkedHashSet} instance. */
  public static <E extends @Nullable Object> CompactLinkedHashSet<E> create() {
    return new CompactLinkedHashSet<>();
  }

  /**

    @Override
    public boolean equals(@Nullable Object other) {
      return (other instanceof ClassWhichIsAlwaysEqualButHasDifferentHashcodes);
    }
  }

  private static class ObjectWhichIsEqualButChangesClass implements Serializable {
    private static final long serialVersionUID = 1L;

    @Override
    public boolean equals(@Nullable Object other) {