*
   * <p>Currently, this method is invoked while holding a lock. If an implementation of this method
   * blocks, it can prevent this service from changing state. If you need to performing a blocking
   * operation in order to trigger shutdown, consider instead registering a listener and
   * implementing {@code stopping}. Note, however, that {@code stopping} does not run at exactly the

import java.util.concurrent.TimeUnit;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * An unbounded {@linkplain BlockingQueue blocking queue} that uses the same ordering rules as class
 * {@link PriorityQueue} and supplies blocking retrieval operations. While this queue is logically
 * unbounded, attempted additions may fail due to resource exhaustion (causing {@code

 * cause DNS services to be accessed. For this reason, you should prefer these methods as much as
 * possible over their JDK equivalents whenever you are expecting to handle only IP address string
 * literals -- there is no blocking DNS penalty for a malformed string.
 *
 * <p>When dealing with {@link Inet4Address} and {@link Inet6Address} objects as byte arrays (vis.

   */
  public static final byte SYN = 22;

  /**
   * End of Transmission Block: A communication control character used to indicate the end of a
   * block of data for communication purposes. ETB is used for blocking data where the block
   * structure is not necessarily related to the processing format.
   *
   * @since 8.0
   */
  public static final byte ETB = 23;

  /**

    }
  }

  static final LazyLogger log = new LazyLogger(AbstractFuture.class);

  // A heuristic for timed gets. If the remaining timeout is less than this, spin instead of
  // blocking. This value is what AbstractQueuedSynchronizer uses.
  private static final long SPIN_THRESHOLD_NANOS = 1000L;

  private static final AtomicHelper ATOMIC_HELPER;

  static {
    AtomicHelper helper;

    /**
     * Records cache misses. This should be called when a cache request returns a value that was not
     * found in the cache. This method should be called by the loading thread, as well as by threads
     * blocking on the load. Multiple concurrent calls to {@link Cache} lookup methods with the same
     * key on an absent value should result in a single call to either {@code recordLoadSuccess} or

    // way for it to return a false negative would be for the target value to jump around in the map
    // such that none of the subsequent iterations observed it, despite the fact that at every point
    // in time it was present somewhere int the map. This becomes increasingly unlikely as
    // CONTAINS_VALUE_RETRIES increases, though without locking it is theoretically possible.

    MemoizingSupplier(Supplier<T> delegate) {
      this.delegate = checkNotNull(delegate);
    }

    @Override
    @ParametricNullness
    public T get() {
      // A 2-field variant of Double Checked Locking.
      if (!initialized) {
        synchronized (this) {
          if (!initialized) {
            T t = delegate.get();
            value = t;
            initialized = true;
            return t;

@GwtCompatible
public enum MultisetFeature implements Feature<Multiset> {
  /**
   * Indicates that elements from {@code Multiset.entrySet()} update to reflect changes in the
   * backing multiset.
   */
  ENTRIES_ARE_VIEWS;

  @Override
  public Set<Feature<? super Multiset>> getImpliedFeatures() {
    return Collections.emptySet();
  }

  @Retention(RetentionPolicy.RUNTIME)
  @Inherited

   * MoreExecutors#newDirectExecutorService} and subject to the same constraints.
   *
   * <p>Although all tasks are immediately executed in the thread that submitted the task, this
   * {@code ExecutorService} imposes a small locking overhead on each task submission in order to
   * implement shutdown and termination behavior.
   *
   * <p>Because of the nature of single-thread execution, the methods {@code scheduleAtFixedRate}