code: @Override
      public boolean cancel(boolean mayInterruptIfRunning) {
          if (RESULT_UPDATER.compareAndSet(this, null, CANCELLATION_CAUSE_HOLDER)) {
              if (checkNotifyWaiters()) {
                  notifyListeners();
              }
              return true;
          }
          return false;
      }
docs: {@inheritDoc}
  
  @param mayInterruptIfRunning this value has no effect in this implementation.