Java Magazine is a bimonthly deep dive into Java and the JVM. Every issue contains explanations about the language and the platform written by experts and members of the Java development team. Contents includes tutorials on new technologies, investigations of alternative JVM languages, explanations of important tools, and lots of advice on coding.
2017 May/June has about 50 pages and features an article on Lombok, JDeferred, Speedment, etc. Check it out!