If you haven’t subscribed to the free Java Magazine published by Oracle then now would be a good time to go do it.
The Nov/Dec issue has a good article about JSoup and WebSockets.
The Sep/Oct issue has a ‘Testing” focus. If you focus on the code supported articles then there is a lot of useful information in the magazine covering JUnit, JavaFX, WebDriver Grid, JMeter.
The magazine is free and published digitally so you can read it online. I recommend you subscribe.