[java] New Rule: Use Explicit Types

[adangel]

Describe the PR

Most basic implementation of #2847.

Please review description and properties...

I've not added it to the quickstart.xml ruleset, as I think, this rule is a bit controversial and depends on the project.

I've chosen "Best Practices" "Code Style" as category and not error prone, as using var doesn't break the code, it's "just harder to read".

Related issues

• Fixes [java] New Rule: Use Explicit Types #2847

Ready?

• Added unit tests for fixed bug/feature
• Passing all unit tests
• Complete build ./mvnw clean verify passes (checked automatically by github actions)
• Added (in-code) documentation (if needed)

[pmd-test]

	1 Message
📖	Compared to master: This changeset changes 0 violations, introduces 35 new violations, 0 new errors and 0 new configuration errors, removes 0 violations, 0 errors and 0 configuration errors. Download full report as build artifact
✅	Compared to master: This changeset changes 0 violations, introduces 35 new violations, 0 new errors and 0 new configuration errors, removes 0 violations, 0 errors and 0 configuration errors. Download full report as build artifact
✅	Compared to master: This changeset changes 5 violations, introduces 35 new violations, 0 new errors and 0 new configuration errors, removes 0 violations, 0 errors and 0 configuration errors. Full report

Generated by 🚫 Danger

[oowekyala]

Thanks!
I think this rule is a better fit for the codestyle category though.
As the java devs put it, explicit types are a trade-off. Sometimes type Inference makes code more readable, and sometimes it's the other way around. Disallowing var is a pretty extreme stance on the issue and I don't think it's a widely accepted one, so I would not classify this rule as a best practice. It might be useful as a coding convention, which is developer- or codebase-specific.