monitor.leave();
    }
  }

  /**
   * Returns an iterator over the elements in this queue. The iterator does not return the elements
   * in any particular order. The returned {@code Iterator} is a "weakly consistent" iterator that
   * will never throw {@link ConcurrentModificationException}, and guarantees to traverse elements
   * as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect

@ElementTypesAreNonnullByDefault
public abstract class FinalizableWeakReference<T> extends WeakReference<T>
    implements FinalizableReference {
  /**
   * 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();

  /**
   * Returns a view of the entries stored in this cache as a thread-safe map. Modifications made to
   * the map directly affect the cache.
   *
   * <p>Iterators from the returned map are at least <i>weakly consistent</i>: they are safe for
   * concurrent use, but if the cache is modified (including by eviction) after the iterator is
   * created, it is undefined which of the changes (if any) will be reflected in that iterator.

   */
  private static class LockGraphNode {

    /**
     * The map tracking the locks that are known to be acquired before this lock, each associated
     * with an example stack trace. Locks are weakly keyed to allow proper garbage collection when
     * they are no longer referenced.
     */
    final Map<LockGraphNode, ExampleStackTrace> allowedPriorLocks =
        new MapMaker().weakKeys().makeMap();

    /**

  `Two days wrong!' sighed the Hatter.  `I told you butter
wouldn't suit the works!' he added looking angrily at the March
Hare.

  `It was the BEST butter,' the March Hare meekly replied.

  `Yes, but some crumbs must have got in as well,' the Hatter
grumbled:  `you shouldn't have put it in with the bread-knife.'

  The March Hare took the watch and looked at it gloomily:  then

      assertBasicInvariants(striped);
    }
  }

  private static void assertBasicInvariants(Striped<?> striped) {
    Set<Object> observed = Sets.newIdentityHashSet(); // for the sake of weakly referenced locks.
    // this gets the stripes with #getAt(index)
    for (int i = 0; i < striped.size(); i++) {
      Object object = striped.getAt(i);
      assertNotNull(object);

  /**
   * Returns a view of the entries stored in this cache as a thread-safe map. Modifications made to
   * the map directly affect the cache.
   *
   * <p>Iterators from the returned map are at least <i>weakly consistent</i>: they are safe for
   * concurrent use, but if the cache is modified (including by eviction) after the iterator is
   * created, it is undefined which of the changes (if any) will be reflected in that iterator.
   *

      return previousWrite;
    }

    @Override
    public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
      this.previousWrite = previous;
    }
  }

  /** Used for weakly-referenced keys. */
  static class WeakEntry<K, V> extends WeakReference<K> implements ReferenceEntry<K, V> {
    WeakEntry(ReferenceQueue<K> queue, K key, int hash, @CheckForNull ReferenceEntry<K, V> next) {

      assertBasicInvariants(striped);
    }
  }

  private static void assertBasicInvariants(Striped<?> striped) {
    Set<Object> observed = Sets.newIdentityHashSet(); // for the sake of weakly referenced locks.
    // this gets the stripes with #getAt(index)
    for (int i = 0; i < striped.size(); i++) {
      Object object = striped.getAt(i);
      assertNotNull(object);

   * Executor#execute execute}, as in {@code ThreadPoolExecutor.CallerRunsPolicy}.
   *
   * <p>This executor is appropriate for tasks that are lightweight and not deeply chained.
   * Inappropriate {@code directExecutor} usage can cause problems, and these problems can be
   * difficult to reproduce because they depend on timing. For example:
   *
   * <ul>