assertTrue(Thread.holdsLock(mutex));
      return super.containsValue(value);
    }

    @Override
    public @Nullable V get(Object key) {
      assertTrue(Thread.holdsLock(mutex));
      return super.get(key);
    }

    @Override
    public @Nullable V put(K key, V value) {
      assertTrue(Thread.holdsLock(mutex));
      return super.put(key, value);
    }

    @Override

import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.jspecify.annotations.Nullable;

/**
 * Utility methods for working with {@link Closeable} objects.
 *
 * @author Michael Lancaster
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
public final class Closeables {

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;

/**
 * Used to test listenable future implementations.
 *
 * @author Sven Mawson
 */
@NullUnmarked
@GwtIncompatible
@J2ktIncompatible
public class ListenableFutureTester {

import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.EnumSet;
import org.jspecify.annotations.Nullable;

/**
 * Implementation of {@link ImmutableSet} backed by a non-empty {@link java.util.EnumSet}.
 *
 * @author Jared Levy
 */
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization

      return standardSubMultiset(lowerBound, lowerBoundType, upperBound, upperBoundType);
    }

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

    @Override
    public boolean equals(@Nullable Object object) {
      return standardEquals(object);
    }

    @Override
    public int hashCode() {
      return standardHashCode();
    }

      table.put('b', "four", 4);
      return table.row('a');
    }
  }

  static final Function<@Nullable Integer, @Nullable Integer> DIVIDE_BY_2 =
      new Function<@Nullable Integer, @Nullable Integer>() {
        @Override
        public @Nullable Integer apply(@Nullable Integer input) {
          return (input == null) ? null : input / 2;
        }
      };

      table.put('b', "four", 4);
      return table.row('a');
    }
  }

  static final Function<@Nullable Integer, @Nullable Integer> DIVIDE_BY_2 =
      new Function<@Nullable Integer, @Nullable Integer>() {
        @Override
        public @Nullable Integer apply(@Nullable Integer input) {
          return (input == null) ? null : input / 2;
        }
      };

import com.google.common.annotations.GwtCompatible;
import java.util.Queue;
import org.jspecify.annotations.Nullable;

/**
 * An Iterator implementation which draws elements from a queue, removing them from the queue as it
 * iterates. This class is not thread safe.
 */
@GwtCompatible
final class ConsumingQueueIterator<T extends @Nullable Object> extends AbstractIterator<T> {
  private final Queue<T> queue;

import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Tests for {@link Multisets#immutableEntry}.
 *
 * @author Mike Bostock
 */
@GwtCompatible
@NullMarked
public class MultisetsImmutableEntryTest extends TestCase {
  private static final @Nullable String NE = null;

  private static <E extends @Nullable Object> Entry<E> entry(E element, int count) {

  public @Nullable K floorKey(K key) {
    return keyOrNull(floorEntry(key));
  }

  @Override
  public @Nullable Entry<K, V> ceilingEntry(K key) {
    return tailMap(key, true).firstEntry();
  }

  @Override
  public @Nullable K ceilingKey(K key) {
    return keyOrNull(ceilingEntry(key));
  }

  @Override
  public @Nullable Entry<K, V> higherEntry(K key) {