I did not know Java, let alone B4J. Same is true for AutoHotkey, in which I have made numerous free portable programs.
What I do is :
I download sample code in the language, say B4J. Then run it. Then run it under debugger and try to understand the flow/logic.
Write in the Forum the part which stumps me. Get answer. Move to next.
Make a new program from scratch in say B4J, and query the thinks which I could not do.
You can try following it.