* tasks. Second, the returned list will always be empty, as any submitted task is considered to
   * have started execution. This applies also to tasks given to {@code invokeAll} or {@code
   * invokeAny} which are pending serial execution, even the subset of the tasks that have not yet
   * started execution. It is unclear from the {@code ExecutorService} specification if these should

                        master.put(key, existing);
                        if (!pending.isEmpty()) {
                            predecessors.put(key, pending);
                            pending = new ArrayList<>();
                        }
                    } else {
                        pending.add(element);
                    }
                }

   * size}, inclusive.
   *
   * @param start a user-supplied index identifying a starting position in an array, list or string
   * @param end a user-supplied index identifying an ending position in an array, list or string
   * @param size the size of that array, list or string
   * @throws IndexOutOfBoundsException if either index is negative or is greater than {@code size},

   * implementation. Using a reconstruction of the default Object.toString() prevents OOMs and stack
   * overflows, and helps avoid sensitive data inadvertently ending up in exception messages.
   */
  private void appendResultObject(StringBuilder builder, @CheckForNull Object o) {
    if (o == null) {
      builder.append("null");
    } else if (o == this) {

                        master.put(key, element);

                        if (!pending.isEmpty()) {
                            predecessors.put(key, pending);
                            pending = new ArrayList<>();
                        }
                    } else {
                        pending.add(element);
                    }
                }