try {
      generateCancellationCauses =
          Boolean.parseBoolean(
              System.getProperty("guava.concurrent.generate_cancellation_cause", "false"));
    } catch (SecurityException e) {
      generateCancellationCauses = false;
    }
    GENERATE_CANCELLATION_CAUSES = generateCancellationCauses;
  }

  /**

      }
    };

    boolean isDone() {
      return true;
    }

    boolean isCancelled() {
      return false;
    }

    void maybeThrowOnGet(@Nullable Throwable cause) throws ExecutionException {}

    boolean permitsPublicUserToTransitionTo(State state) {
      return false;
    }
  }

  private static final class Listener {
    final Runnable command;
    final Executor executor;