Code quality improvement and codebase optimization

[BenCheung0422]

For various reasons, the code quality should be improved, including formats, coding practices and error handlings. This includes making good use of standard libraries like Google Guava, Apache Commons, etc., reducing unnecessary blocks of codes and optimizing the codebase. The JavaDoc commenting style should also be united, an example can be taken from #579. Ideally, any potential errors and exceptions should be caught and handled properly, minimizing the chances getting unhandled errors, uninformative reports and unideal fallbacks/case handlings, thus making it cooperative with the upcoming crash report system (#461). This may need time to be come over.

[Makkkkus]

Over a year old. Has no comments.

I disagree that new libraries should be introduced to reduce "unneccecary blocks of codes and optimizing the database". New libraries usually add "unneccecary blocks of codes", as you usually have to compile and distribute the entire library when using it.

Ideally, any potential errors and exceptions should be caught and handled properly, minimizing the chances getting unhandled errors, uninformative reports and unideal fallbacks/case handlings

I also agree that there should be less errors in the project, but since this is so common sense, I don't think this needs to be said.

This does also not propose anything substantial and thus I think this should be closed.