return CollectionTestSuiteBuilder.using(
            new TestStringCollectionGenerator() {
              @Override
              public Collection<@Nullable String> create(@Nullable String[] elements) {
                List<@Nullable String> list = new ArrayList<>();
                for (String element : elements) {
                  list.add((element == null) ? null : "q" + element);
                }

 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingMultiset<E extends @Nullable Object> extends ForwardingCollection<E>
    implements Multiset<E> {

  /** Constructor for use by subclasses. */
  protected ForwardingMultiset() {}

  @Override
  protected abstract Multiset<E> delegate();

  @Override
  public int count(@Nullable Object element) {
    return delegate().count(element);
  }

import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.util.HashSet;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * Based on what a {@link Type} is, dispatch it to the corresponding {@code visit*} method. By
 * default, no recursion is done for type arguments or type bounds. But subclasses can opt to do

@SuppressWarnings("JUnit4ClassUsedInJUnit3")
@NullMarked
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();

@SuppressWarnings("JUnit4ClassUsedInJUnit3")
@NullMarked
public abstract class AbstractBiMapTester<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMapTester<K, V> {

  @Override
  protected BiMap<K, V> getMap() {
    return (BiMap<K, V>) super.getMap();
  }

  static <K extends @Nullable Object, V extends @Nullable Object> Entry<V, K> reverseEntry(
      Entry<K, V> entry) {

 * limitations under the License.
 */

package com.google.common.collect.testing;

import com.google.common.annotations.GwtCompatible;
import org.jspecify.annotations.Nullable;

/**
 * An unhashable object to be used in testing as values in our collections.
 *
 * @author Regina O'Dell
 */
@GwtCompatible
public class UnhashableObject implements Comparable<UnhashableObject> {

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import org.jspecify.annotations.Nullable;

/**
 * Soft reference with a {@code finalizeReferent()} method which a background thread invokes after
 * the garbage collector reclaims the referent. This is a simpler alternative to using a {@link
 * ReferenceQueue}.

 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.common.collect;

import java.util.Collection;
import org.jspecify.annotations.Nullable;

/** Never actually created; instead delegates to JdkBackedImmutableMultiset. */
final class RegularImmutableMultiset<E> extends ImmutableMultiset<E> {
  static final ImmutableMultiset<Object> EMPTY =

// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
@NullMarked
public class SetMultimapAsMapTester<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMultimapTester<K, V, SetMultimap<K, V>> {
  public void testAsMapValuesImplementSet() {
    for (Collection<V> valueCollection : multimap().asMap().values()) {

  public void testWildcardFuture() {
    SettableFuture<String> settable = SettableFuture.create();
    ListenableFuture<?> f = settable;
    FutureCallback<@Nullable Object> callback =
        new FutureCallback<@Nullable Object>() {
          @Override
          public void onSuccess(@Nullable Object result) {}

          @Override
          public void onFailure(Throwable t) {}
        };
    addCallback(f, callback, directExecutor());