Myself

Working as a machine learning engineer+MLOps, very proficient with python, and some experience with C++, Rust, also did some Scala programming (mostly for big data and spark).

Situation

Joining a new company (hedge fund) as a data engineer, although the data team mostly uses Python, the trading and market connectivity team uses a java stack.

Goal

What would be the best resources to pick up Java in a couple of months to a level where I can read through production codes to make sense and understand intents, and do small refactorings?
Particularly, the class and module structures, along with the build systems seem a bit tricky.

I hope I don’t have to learn as a complete noob in programming but can take a fast track. Any rough roadmap of topics to cover will be sincerely appreciated.