Ololade Badmus well if you want to solve a problem you can solve it without a programming language. That's what I do most of the time -> forcing myself to solve it 'highlevel' on a sheet of paper or such. If it's not a language specific thing.
Banks are actually often pretty boring and highly pseudo political (money and egos). Still, often there are good devs in there. Mainly because they have the money to afford them. it's just stochastics not a judgement that you won't find them somewhere else.
But I don't want to bore you to much.
Just keep in mind that tribalism is a human thing and every group always sees where they are great and others are bad.
And to kick in one of my favorite quotes on the idea that there are only wrong answers in life:
All models are wrong, but some are useful
depends on the focus. I general Java is a more renown backend language and js is often a synonym for frontend. Also if you know java everyone assumes that javascript is going to be easy for you.
In reality both of them are still going to be optimized for example the gralVM of oracle will compile your JS, java and python code into 1 with JIT optimizations so the ffi costs are gone. At least a friend of mine is working on that at the moment. I won't go into the details because A: I just understand the concept and some problems of it. and B: because it's kinda off topic
I am a backend engineer and esp algorithms and data-structures are very important to me. Personally I know and like both language the same. Java has certain advantages and JS has certain advantages. Proficiency and other things also get important, the language you are more used to usually is the default language.
pointing towards your OOP-Design Question .... if you pick java you have little to no way around OOP-Design in your professional life. the GoF is basically rooted in Java and C#.
However as a disclaimer .... I love languages that's why I write in multiple different ones and do not participate in language-religions (anymore). if it's touring complete it works. However Java opens you different doors than Javascript. it is a stereotype but javascript people often are still seen as script kiddies.
This has a core reason rooted in the js community value: Beginner friendly. It's true and not true at the same time. I just want to point out, that there is pseudo elitism of languages towards certain attributes languages can have
just as some examples.
So here's the actually conclusion of me trying to explain my train of thought:
This is my europe-centric view. I can only talk about that. No clue if america or any other continent/country is different.