return !queue.isEmpty();
    }

    @Override
    @ParametricNullness
    public T next() {
      IndexedIterator<T> nextIndexed = queue.remove();
      PeekingIterator<T> nextIter = nextIndexed.iterator;
      T next = nextIter.next();
      if (nextIter.hasNext()) {
        queue.add(nextIndexed);
      }
      return next;
    }
  }

  static <K, V> CountingRemovalListener<K, V> countingRemovalListener() {
    return new CountingRemovalListener<>();
  }

  /** {@link RemovalListener} that adds all {@link RemovalNotification} objects to a queue. */
  @J2ktIncompatible
  @GwtIncompatible // ConcurrentLinkedQueue
  static class QueuingRemovalListener<K, V> extends ConcurrentLinkedQueue<RemovalNotification<K, V>>
      implements RemovalListener<K, V> {

		},
		config.HelpKV{
			Key:         target.AmqpAutoDeleted,
			Description: "auto delete queue when set to 'on', when there are no consumers",
			Optional:    true,
			Type:        "on|off",
		},
		config.HelpKV{
			Key:         target.AmqpDeliveryMode,
			Description: "set to '1' for non-persistent or '2' for persistent queue",
			Optional:    true,
			Type:        "number",
		},
		config.HelpKV{

import com.google.common.collect.testing.features.CollectionSize;
import java.util.NoSuchElementException;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code remove()} operations on a queue. Can't be invoked
 * directly; please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
 *
 * @author Jared Levy
 */
@GwtCompatible

	Region     string           `json:"region"`
	Worm       config.BoolFlag  `json:"worm"`

	// Storage class configuration
	StorageClass storageclass.Config `json:"storageclass"`

	// Notification queue configuration.
	Notify notify.Config `json:"notify"`

	// Logger configuration
	Logger logger.Config `json:"logger"`

	// Compression configuration
	Compression compress.Config `json:"compress"`

import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code peek()} operations on a queue. Can't be invoked directly;
 * please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
 *
 * @author Jared Levy
 */
@GwtCompatible

import java.util.NavigableSet;
import java.util.Optional;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.OptionalLong;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Random;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.UUID;

import com.google.common.util.concurrent.AbstractFutureBenchmarks.OldAbstractFuture;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import java.util.LinkedList;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executor;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadPoolExecutor;

import java.util.LinkedList;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;

/**
 * Tests for {@link Synchronized#deque} and {@link Queues#synchronizedDeque}.
 *
 * @author Kurt Alfred Kluever
 */
@NullUnmarked
public class SynchronizedDequeTest extends TestCase {

  protected Deque<String> create() {
    TestDeque<String> inner = new TestDeque<>();

 *   <li>{@link Iterators}
 *   <li>{@link Lists}
 *   <li>{@link Maps}
 *   <li>{@link MoreCollectors}
 *   <li>{@link Multimaps}
 *   <li>{@link Multisets}
 *   <li>{@link ObjectArrays}
 *   <li>{@link Queues}
 *   <li>{@link Sets}
 *   <li>{@link Streams}
 *   <li>{@link Tables}
 * </ul>
 *
 * <h2>Abstract implementations</h2>
 *
 * <ul>
 *   <li>{@link AbstractIterator}