List of sonar warnings to correct:

1. https://sonarcloud.io/project/issues?id=com.puppycrawl.tools%3Acheckstyle&open=AWkisA05gtFwgfOLg-aa&resolved=false&severities=MINOR&types=CODE_SMELL
2. https://sonarcloud.io/project/issues?id=com.puppycrawl.tools%3Acheckstyle&open=AWb-Jn2kTJjFgJLTEG8I&resolved=false&severities=MAJOR&types=CODE_SMELL
3. https://sonarcloud.io/project/issues?id=com.puppycrawl.tools%3Acheckstyle&open=AWb-Jn2kTJjFgJLTEG8I&resolved=false&severities=MAJOR&types=CODE_SMELL
4. https://sonarcloud.io/project/issues?id=com.puppycrawl.tools%3Acheckstyle&open=AV3yuSS3pvRVEt3b0XpD&resolved=false&severities=MINOR&types=CODE_SMELL

Also change following code for more functional style:

1. checkstyle/src/main/java/com/puppycrawl/tools/checkstyle/checks/TranslationCheck.java

   Lines 263 to 267 in 51bf6a6

   	final Optional<String> fileName = getMissingFileName(bundle, null);
   	if (fileName.isPresent()) {
   	logMissingTranslation(bundle.getPath(), fileName.get());
   	}
   	}

2. checkstyle/src/main/java/com/puppycrawl/tools/checkstyle/checks/TranslationCheck.java

   Lines 278 to 281 in 51bf6a6

   	final Optional<String> fileName = getMissingFileName(bundle, languageCode);
   	if (fileName.isPresent()) {
   	logMissingTranslation(bundle.getPath(), fileName.get());
   	}