Cell[] as;
      Cell a;
      int n;
      long v;
      if ((as = cells) != null && (n = as.length) > 0) {
        if ((a = as[(n - 1) & h]) == null) {
          if (busy == 0) { // Try to attach new Cell
            Cell r = new Cell(x); // Optimistically create
            if (busy == 0 && casBusy()) {
              boolean created = false;
              try { // Recheck under lock
                Cell[] rs;

      Cell[] as;
      Cell a;
      int n;
      long v;
      if ((as = cells) != null && (n = as.length) > 0) {
        if ((a = as[(n - 1) & h]) == null) {
          if (busy == 0) { // Try to attach new Cell
            Cell r = new Cell(x); // Optimistically create
            if (busy == 0 && casBusy()) {
              boolean created = false;
              try { // Recheck under lock
                Cell[] rs;

      Cell[] as;
      Cell a;
      int n;
      long v;
      if ((as = cells) != null && (n = as.length) > 0) {
        if ((a = as[(n - 1) & h]) == null) {
          if (busy == 0) { // Try to attach new Cell
            Cell r = new Cell(x); // Optimistically create
            if (busy == 0 && casBusy()) {
              boolean created = false;
              try { // Recheck under lock
                Cell[] rs;

   * the discussion in the {@link #addListener} documentation. All its warnings about heavyweight
   * listeners are also applicable to heavyweight callbacks passed to this method.
   *
   * <p>For a more general interface to attach a completion listener, see {@link #addListener}.
   *
   * <p>This method is similar to {@link java.util.concurrent.CompletableFuture#whenComplete} and

      Cell[] as;
      Cell a;
      int n;
      long v;
      if ((as = cells) != null && (n = as.length) > 0) {
        if ((a = as[(n - 1) & h]) == null) {
          if (busy == 0) { // Try to attach new Cell
            Cell r = new Cell(x); // Optimistically create
            if (busy == 0 && casBusy()) {
              boolean created = false;
              try { // Recheck under lock
                Cell[] rs;

         *
         * In theory, cancel() could execute arbitrary listeners -- bad to do while holding a lock.
         * However, we don't expose currentFuture to users, so they can't attach listeners. And the
         * Future might not even be a ListenableFuture, just a plain Future. That said, similar
         * problems can exist with methods like FutureTask.done(), not to mention slow calls to

   * that need to listen to more fine-grained events (such as when each particular {@linkplain
   * Service service} starts, or terminates), should attach {@linkplain Service.Listener service
   * listeners} to each individual service.
   *
   * @author Luke Sandberg
   * @since 15.0 (present as an interface in 14.0)
   */
  public abstract static class Listener {

   * that need to listen to more fine-grained events (such as when each particular {@linkplain
   * Service service} starts, or terminates), should attach {@linkplain Service.Listener service
   * listeners} to each individual service.
   *
   * @author Luke Sandberg
   * @since 15.0 (present as an interface in 14.0)
   */
  public abstract static class Listener {

   * the discussion in the {@link #addListener} documentation. All its warnings about heavyweight
   * listeners are also applicable to heavyweight callbacks passed to this method.
   *
   * <p>For a more general interface to attach a completion listener, see {@link #addListener}.
   *
   * <p>This method is similar to {@link java.util.concurrent.CompletableFuture#whenComplete} and

         *
         * In theory, cancel() could execute arbitrary listeners -- bad to do while holding a lock.
         * However, we don't expose currentFuture to users, so they can't attach listeners. And the
         * Future might not even be a ListenableFuture, just a plain Future. That said, similar
         * problems can exist with methods like FutureTask.done(), not to mention slow calls to