* everywhere.
     */
    static final class Sync<V> extends AbstractQueuedSynchronizer {

      private static final long serialVersionUID = 0L;

      /* Valid states. */
      static final int RUNNING = 0;
      static final int COMPLETING = 1;
      static final int COMPLETED = 2;
      static final int CANCELLED = 4;
      static final int INTERRUPTED = 8;