XChange-stream is a Java library providing a simple and consistent streaming API for interacting with Bitcoin and other crypto currency exchanges via WebSocket protocol. It is build on top of of XChange library providing new interfaces for streaming API. User can subscribe for live updates via reactive streams of RxJava library.
Any plans to support https://www.gdax.com/? it has a fix and rest websocket, documented here:https://docs.gdax.com/#websocket-feed and here: https://docs.gdax.com/#fix-api.