//    monitor.enterXXX()/monitor.leave() will make it really clear
  //    which lock is held at any point in the code.
  //
  // 3. I think "enterWhen(notEmpty)" reads better than "notEmpty.enter()".
  //
  // TODO(user): Implement ReentrantLock features:
  //    - toString() method
  //    - getOwner() method
  //    - getQueuedThreads() method

        stack = stack.next;
      }
    }

    private static class RunnableExecutorPair {
      final Runnable runnable;
      final Executor executor;
      // Volatile because this is written on one thread and read on another with no synchronization.
      @Nullable volatile RunnableExecutorPair next;

      RunnableExecutorPair(@Nullable Runnable runnable, @Nullable Executor executor) {
        this.runnable = runnable;

                  }
                  /*
                   * Also look up an earlier node so that, if the graph is using MapRetrievalCache,
                   * we read one of the fields declared in that class.
                   */
                  Set<Integer> unused = graph.successors(first);
                  return null;
                }
              }));
    }

    return CollectCollectors.toMultiset(elementFunction, countFunction, multisetSupplier);
  }

  /**
   * Returns an unmodifiable view of the specified multiset. Query operations on the returned
   * multiset "read through" to the specified multiset, and attempts to modify the returned multiset
   * result in an {@link UnsupportedOperationException}.
   *

   *     RuntimeException(e)}. But consider whether users would be better off if your API threw a
   *     different type of exception. For background on the deprecation, read <a
   *     href="https://goo.gl/Ivn2kc">Why we deprecated {@code Throwables.propagate}</a>.
   */
  @CanIgnoreReturnValue
  @J2ktIncompatible
  @GwtIncompatible
  @Deprecated

/**
 * An immutable array of {@code int} values, with an API resembling {@link List}.
 *
 * <p>Advantages compared to {@code int[]}:
 *
 * <ul>
 *   <li>All the many well-known advantages of immutability (read <i>Effective Java</i>, third
 *       edition, Item 17).
 *   <li>Has the value-based (not identity-based) {@link #equals}, {@link #hashCode}, and {@link
 *       #toString} behavior you expect

   *     RuntimeException(e)}. But consider whether users would be better off if your API threw a
   *     different type of exception. For background on the deprecation, read <a
   *     href="https://goo.gl/Ivn2kc">Why we deprecated {@code Throwables.propagate}</a>.
   */
  @CanIgnoreReturnValue
  @J2ktIncompatible
  @GwtIncompatible
  @Deprecated

/**
 * An immutable array of {@code double} values, with an API resembling {@link List}.
 *
 * <p>Advantages compared to {@code double[]}:
 *
 * <ul>
 *   <li>All the many well-known advantages of immutability (read <i>Effective Java</i>, third
 *       edition, Item 17).
 *   <li>Has the value-based (not identity-based) {@link #equals}, {@link #hashCode}, and {@link
 *       #toString} behavior you expect.

 * Provides static methods for working with {@code Collection} instances.
 *
 * <p><b>Java 8+ users:</b> several common uses for this class are now more comprehensively
 * addressed by the new {@link java.util.stream.Stream} library. Read the method documentation below
 * for comparisons. These methods are not being deprecated, but we gently encourage you to migrate
 * to streams.
 *
 * @author Chris Povirk
 * @author Mike Bostock
 * @author Jared Levy

 * <p>Keys and values may be null. All optional multimap methods are supported, and all returned
 * views are modifiable.
 *
 * <p>This class is not threadsafe when any concurrent operations update the multimap. Concurrent
 * read operations will work correctly. To allow concurrent update operations, wrap your multimap
 * with a call to {@link Multimaps#synchronizedSetMultimap}.
 *