Verifying the answer to push notification with Java API

How can I get the answer user provides to the push notification through their phone with Java SDK? It requires transactionId in addition to other parameters used in verification of other factors as far as I understand. But where to set this?

ExtensibleResource resource = client.instantiate(ExtensibleResource.class);
ExtensibleResource protocolNode = client.instantiate(ExtensibleResource.class);
protocolNode.put("type", "OAUTH");
resource.put("protocol", protocolNode);
ExtensibleResource result = client.http().get(pollUrl, ExtensibleResource.class);