I am working on a small project for school and want to share it with you. Can you give me some feedback on it? It is a payroll system in which you can register, view and delete employees and also generate payslips. Is my first ever project and I am somehow proud of it but I want to see what optimizations I can make to it if you are so kind to spare a few minutes of your busy life. o7 commanders :P
Here is the link to the GitHub: https://github.com/iiulian8/...

Quick suggestion.

Try to break up the main method into smaller, well named functions.

Try to keep each function less than a page if possible and with at most 2 nested levels.

Smaller methods will be easier to follow and well named function act as in code documentation.

An example: if you have an if with two large parts, break each part into its own method with a descriptive name.

The logic of the if statement will be much easier to see and check for errors.

Same with loops with much content, put the loop in its own function.

Mocup example in no real language :)

Main()
setup();
ProgramLoop();

ProgramLoop()
While(!quit)
Process(GetInput())

And, make sure to keep both versions

Just in case the rewrite does not work.

Other than that, looks quite a lot like one of my first programs, but not quite as bloated with unnecessary features ;)

The features are part of the assignment.... they are a pain. Thank you very much for the feedback ;)

Heres a tip, instead of
ArrayList<peepeepoopoo> a = ...

You can

var a = new Arrayslist...

You can call the super-Constructor from the subclasses constructors.

That humongous main method is not a good idea.

Add a README.md, add the .idea and out folders to a .gitignore, just small git related observations ;)