*       {@code equals()}, {@code hashCode()}, and graph equivalence</a>
 *   <li><a href="https://github.com/google/guava/wiki/GraphsExplained#synchronization">
 *       Synchronization policy</a>
 *   <li><a href="https://github.com/google/guava/wiki/GraphsExplained#notes-for-implementors">Notes
 *       for implementors</a>
 * </ul>
 *
 * @author James Sexton

   * usually have much noticeable impact. A value of one permits only one thread to modify the map
   * at a time, but since read operations can proceed concurrently, this still yields higher
   * concurrency than full synchronization. Defaults to 4.
   *
   * <p><b>Note:</b> Prior to Guava release 9.0, the default was 16. It is possible the default will
   * change again in the future. If you care about this value, you should always choose it

 *       {@code equals()}, {@code hashCode()}, and graph equivalence</a>
 *   <li><a href="https://github.com/google/guava/wiki/GraphsExplained#synchronization">
 *       Synchronization policy</a>
 *   <li><a href="https://github.com/google/guava/wiki/GraphsExplained#notes-for-implementors">Notes
 *       for implementors</a>
 * </ul>
 *
 * @author James Sexton

        default:
          throw new AssertionError("unexpected state: " + state);
      }
    }
  }

  abstract static class OldAbstractFuture<V> implements ListenableFuture<V> {

    /** Synchronization control for AbstractFutures. */
    private final Sync<V> sync = new Sync<V>();

    // The execution list to hold our executors.
    private final ExecutionList executionList = new ExecutionList();

        default:
          throw new AssertionError("unexpected state: " + state);
      }
    }
  }

  abstract static class OldAbstractFuture<V> implements ListenableFuture<V> {

    /** Synchronization control for AbstractFutures. */
    private final Sync<V> sync = new Sync<V>();

    // The execution list to hold our executors.
    private final ExecutionList executionList = new ExecutionList();

 * #runOneIteration} takes longer than its schedule defines, then subsequent executions may start
 * late. Also, all life cycle methods are executed with a lock held, so subclasses can safely modify
 * shared state without additional synchronization necessary for visibility to later executions of
 * the life cycle methods.
 *
 * <h3>Usage Example</h3>
 *
 * <p>Here is a sketch of a service which crawls a website and uses the scheduling capabilities to

 *
 * <p>If {@code null} is passed as the {@code mutex} parameter to any of this class's top-level
 * methods or inner class constructors, the created object uses itself as the synchronization mutex.
 *
 * <p>This class should be used by other collection classes only.
 *
 * @author Mike Bostock
 * @author Jared Levy
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
/*

 * guarantee that the new value will be fully visible to the other threads. To guarantee that
 * modifications are visible, synchronize access to the table. Unlike other {@code Table}
 * implementations, synchronization is unnecessary between a thread that writes to one cell and a
 * thread that reads from another.
 *
 * <p>See the Guava User Guide article on <a href=

   * termination, or other problems, {@code to} may not be a complete copy of {@code from}. If you
   * need to guard against those conditions, you should employ other file-level synchronization.
   *
   * <p><b>Warning:</b> If {@code to} represents an existing file, that file will be overwritten
   * with the contents of {@code from}. If {@code to} and {@code from} refer to the <i>same</i>

 * guarantee that the new value will be fully visible to the other threads. To guarantee that
 * modifications are visible, synchronize access to the table. Unlike other {@code Table}
 * implementations, synchronization is unnecessary between a thread that writes to one cell and a
 * thread that reads from another.
 *
 * <p>See the Guava User Guide article on <a href=