code: public static <V> ListenableFuture<V> immediateFuture(@Nullable V value) {
      return new ImmediateSuccessfulFuture<V>(value);
    }
docs: Creates a {@code ListenableFuture} which has its value set immediately upon
  construction. The getters just return the value. This {@code Future} can't
  be canceled or timed out and its {@code isDone()} method always returns
  {@code true}.