Java Peripheral Resources?

Question

Java

Good afternoon!
Please tell me courses or online resources dedicated to the interaction of external devices with the processor using Java (and if you know the Java + Rasberry Pi bundle, it will be very cool!).
I myself am the customer of this project: I found young guys in my city whose eyes lit up when describing the task, but they have little experience working directly with the hardware (before that, applications and games were written well in Java). I want to give these courses/resources to contractors and my programmers who can in microcontrollers and C, but not in Java.
PS: if there is something similar to JavaRush or CodeWars, then I will try to do it myself in my free time.
PPS: in the near future a bunch of external devices with C ++ is planned - a similar request on this issue.
Thank you very much in advance!