code: public static <A> FutureCallback<A> futureCallback(final Action<A> success, final Action<Throwable> failure) {
          return new FutureCallback<A>() {
              @Override public void onSuccess(A result) {
                  checkNotNull(success).apply(result);
              }
  
              @Override public void onFailure(Throwable t) {
                  checkNotNull(failure).apply(t);
              }
          };
      }
docs: Creates Guava's {@link FutureCallback} from provided Actions