Java Generics

Java Generics and Collections is one of the best resources for the topic.

I summarized it as a mind map of the Generics related concepts here

Java Concurrency Mind Map

Java Concurrency in Practice by Brian Goetz et. al. is one of the best books on Java Concurrency. Nothing else that comes even close to it.

In the last month or so I re-read and summarized it as a Mind Map. You can take a look at it from this link