For the longest time, I was primarily focused on the Spring ecosystem.
Then, over the last two years, I grew the library to teach most foundational aspects of Java development. 
All of these are core building blocks - the project build, understanding testing really well, having a good handle on data structures, logging, Streams, SOLID principles. 
And a lot more.

AI is next, of course.
I'm announcing the agentic learning path in the course roadmap over the next few weeks.  
Learning to use it well is critical for any developer working professionally: 
>> Baeldung All Access


Cheers, 
Eugen.