CheckerFramework was applied to project in scope of #12164

in scope of this issue we need to fix violations that are reasonable.
Here is suppression list https://github.com/checkstyle/checkstyle/tree/master/config/checker-framework-suppressions

We need each remove suppression xml block, run corresponding checker scripts and resolve violation kin main code.
It is highly recommended to use one PR for one violation as fix might be controversial.

~/java/github/checkstyle 
$ groovy ./.ci/checker-framework.groovy --list
Supported profiles:
checker-methods-resource-fenum
checker-nullness-optional-interning
checker-purity-value-returns
checker-formatter
checker-index
checker-signature-gui-units-init
checker-regex-property-key-compiler-message
checker-lock-tainting

name of profile is matching with name of file where suppressions are stored.

Example of expected fix: #14085

ATTENTION: after execution of chekerframework script on local (example: groovy ./.ci/checker-framework.groovy checker-nullness-optional-interning) please restore all comment tags in xml files. We should not remove them.