Last week, I gave a Java 8 course for some colleagues. All the explanations, examples and code samples of that course are available at Github. Feel free to use this material for learning or giving a course of your own. Please give feedback if you find any errors or I forgot a topic. Here are the contents of the course:

1. concepts of Java 1.5: Generics, for-each-loop and varargs
2. functional interfaces and lambdas + exercises
3. default methods
4. method references + exercises
5. streams + exercises
6. Classifying streams
7. Date and Time API + exercises
8. Concurrency
9. Annotations
10. JavaFX
11. Other stuff
12. MissionControl
13. Outlook

All files in this repository are under Creative Commons 4.0.

TL;DR

Learn Java 8 or give a course about it. Have fun!

(Photo: Java logo and wordmark)