Feature Request/Idea: Remove unused imports and methods

[bencomp]

Overview of the Feature Request

Code that is never executed within Dataverse and that is unreachable from outside Dataverse should be removed. Unused imports should also be removed.

What kind of user is the feature intended for?
Developers

What inspired the request?
Many files in the codebase are messy and have low test coverage. But because of the messiness, it is hard to see what should be covered by tests.

This is also part of my all-time quest to improve the codebase, started a long time ago.

What existing behavior do you want changed?
No behaviour should change.

Any brand new behavior do you want to add to Dataverse?
No behaviour needs to be added.

Any open or closed issues related to this feature request?

• Code style: use generics everywhere, remove dead code, resource leaks, javadoc etc. #775 is the original code style issue
• Remove unused GPL-licensed code #9009 is an example that unused code can be removed
• Set up Sonar #9846 and Set up Sonar #9847 should help keep up the quality by monitoring unused imports and methods

[bencomp]

I had a big PR to remove all unused imports and (private) methods, but predictably, while other PRs were merged, merge conflicts would occur. So I closed it. My new plan is to make sure that any PR I create has all unused imports removed.

I suppose we could adjust the Checkstyle file to check for this too, so that contributors are made aware by reviewdog that there are unused imports.

[pdurbin]

While we're add it, should we consider switching to wildcard imports? We don't have any guidance against it at https://guides.dataverse.org/en/6.0/developers/coding-style.html

See also https://stackoverflow.com/questions/147454/why-is-using-a-wild-card-with-a-java-import-statement-bad