Cleanup

[aleksandy]

• use toAray(IntFunction) instead of toArray(T[])
• optimize JavaExtensions#remove()
• simplify JavaExtensions#pad()
• simplify JavaExtensions#join()
• use primitives instead of wrappers
• use pattern matching instead of explicit cast
• use String.valueOf() and toString() for the objects stringification instead of concatenation with empty string

[aleksandy]

@xael-fry, @asolntsev, could you review my PR?

[xael-fry]

The MR is so called "cleanup" but it contains refactors,, fixes and all all parts off the code and not on a given part.
Please split your work in different MR, you can also use the conventional commit to have better description of the scope of the modification apply to.

Thanks

[aleksandy]

I've updated the PR. Removed the replacement of Stack with Deque. The rest of the changes, in my opinion, are quite suitable for a cleanup. Old unused code was removed, some was rewritten using modern capabilities of the standard library and the language.

[aleksandy]

@xael-fry, any news about PR?