private final Executor executor;

  @GuardedBy("queue")
  private final Deque<Runnable> queue = new ArrayDeque<>();

  /** see {@link WorkerRunningState} */
  @LazyInit
  @GuardedBy("queue")
  private WorkerRunningState workerRunningState = IDLE;

  /**
   * This counter prevents an ABA issue where a thread may successfully schedule the worker, the
   * worker runs and exhausts the queue, another thread enqueues a task and fails to schedule the

  /**
   * Constructs a new finalizable weak reference.
   *
   * @param referent to weakly reference
   * @param queue that should finalize the referent
   */
  protected FinalizableWeakReference(@CheckForNull T referent, FinalizableReferenceQueue queue) {
    super(referent, queue.queue);
    queue.cleanUp();
  }

import java.util.Collection;
import java.util.Iterator;
import java.util.Queue;
import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@link Synchronized#queue} and {@link Queues#synchronizedQueue}.
 *
 * @author Kurt Alfred Kluever
 */
public class SynchronizedQueueTest extends TestCase {

  protected Queue<String> create() {
    TestQueue<String> inner = new TestQueue<>();

import java.util.Queue;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Creates queues, containing sample elements, to be tested.
 *
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface TestQueueGenerator<E extends @Nullable Object> extends TestCollectionGenerator<E> {
  @Override
  Queue<E> create(Object... elements);

   * {@link Iterators#consumingIterator(Iterator)}.
   *
   * <p>Note: If {@code iterable} is a {@link Queue}, the returned iterable will instead use {@link
   * Queue#isEmpty} and {@link Queue#remove()}, since {@link Queue}'s iteration order is undefined.
   * Calling {@link Iterator#hasNext()} on a generated iterator from the returned iterable may cause

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

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

import com.google.common.collect.Lists;
import com.google.common.util.concurrent.AbstractFutureBenchmarks.OldAbstractFuture;
import com.google.errorprone.annotations.concurrent.GuardedBy;
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 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

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;

/**
 * A bounded {@linkplain BlockingQueue blocking queue} backed by an array. This queue orders
 * elements FIFO (first-in-first-out). The head of the queue is that element that has been
 * on the queue the longest time. The tail of the queue is that element that has been on
 * the queue the shortest time. New elements are inserted at the tail of the queue, and the queue
 * retrieval operations obtain elements at the head of the queue.