I learned Java when I went to school for a CS degree. It was the only language the school taught, but I picked up on Python after a few years since I was hungry to learn programming haha.
What you describe sounds like the usual imposture syndrome.
Now if your college teaches Java they will probably teach you what you need todo for a Rock paper scissors game (if its not like some crazy GUI, but command line interface) so don’t think your a failure if you don’t figure it out in a week. It took me at least 2 years of going to school to even be presented with that challenge!
It’s fine if you want to get ahead, and its great that your curious and want to learn, but don’t think you must learn it and get it working or your a failure. Learning programming is hard, and it takes time.
Now, there won’t be a point when you feel like you know it 100%. You probably will be able to get to a point where you can say “I can build a rock paper scissors game no problem” but odds are you will still get tripped up on small stuff here and there (type, compile error, bug with your random number generation, etc) even when you already have tons of programming experience. That doesn’t mean you a failure, it just means your human.
You can only be as ready as you can be, so don’t think you have to pass some imaginary bar all the time. Just try ytour best, and if you run into problems, you keep going until you overcome it. So if your having trouble with writing your game, figure out why your having trouble, break it down and search for answers (google, stack overflow, read the docs, etc). The fact your having trouble and struggling is normal, its how you learn. If you didn’t have trouble, ether thru dumb luck, or your code is somehow perfect the first time, you probably wouldn’t learn much. The issues you learn to overcome is the experience you use down the line.
Goodluck, keep building, keep grinding
When I started learning programming I always said I learned by bashing my head against the compiler and bugs until they cracked haha!
PS. Idk the actual complexity of your game, but a rock paper scissors game that takes user input isn’t complex enough for anything more complex than a few lines of code. No need for objects, classes, or any fancy Object Oriented Programming stuff. I’d maybe tackle another problem that is more complex, and might be better done with OOP methods