I just wanted to give a heads-up on pr/5319 , which makes sdks-java-core ErrorProne-clean and upgrades ErrorProne analysis to produce build errors.
ErrorProne  is another static analysis tool which hooks into the Java compilation process. Kenn added it as warnings during the Gradle migration  and it found a number of issues. The issues were easy to fix and in my opinion provide real value.
ErrorProne analysis is enabled for most other modules, but produces warnings instead of errors. I encourage others to take a look at modules they maintain and see if they can similarly enable warnings-as-errors to keep modules ErrorProne-clean.