You also raised a ticket with a similar question that also asked about using Python to validate an email address.
Per my response on the ticket, I cannot really comment on the Java issues but I thought I would post the example of using Python scripting in a Transform node, in case it is useful to the community. Perhaps someone in the community who is familiar with Java could comment on your original enquiry.
ConfigureFields script:

ProcessRecords script:

Which generates the following results:

Attached files
Check_Fields_for_Valid_Email - 6 Jul 2021.lna