Pub/Sub ApiFutures.addCallback() deprecated

What should people use to add an asynchronous callback on the Api Futures instead now since it's deprecated? 

https://github.com/googleapis/google-cloud-java/blob/9cc799fcf68c82ab431d425fefa58ef615ce8e5b/google-cloud-examples/src/main/java/com/google/cloud/examples/pubsub/snippets/CreateTopicAndPublishMessages.java#L103