We had warnings showing up still on Jenkins after changing our build over to treat all Javadoc warnings as errors.

In investigating how that was possible, we found the following warning:

[ImmutableEnumChecker] enums should be immutable: 'Type' has field 'mime' of type 'com.acme.MyEnumType', the declaration of type 'com.acme.MyEnumType' is not annotated with @com.google.errorprone.annotations.Immutable

But that is coming from the Java compiler, or specifically from Error Prone, not from Javadoc. I assume it's because it happens to mention an annotation, which contains the @ typically also seen in Javadoc.

Another build has the same problem, except every warning is misidentified as being from JavaDoc.

[UnitTestGroup2] 2019-01-08 14:02:07 /opt/data/jenkins/Pipeline-Bitbucket/core@2/processing/src/java/com/acme/export/print/AbstractPdfExporter.java:54: warning: [deprecation] createTmpDirectory(String) in FileUtils has been deprecated

In this case, there is also a @ sign, but this time it's part of the file path for the project directory, which isn't anything I have control over even.