VeraPDF (https://verapdf.org) is the primary open-source tool to verify PDF/A documents and it's written in Java. It contains a GUI and a command line variant to verify PDF/A documents.
LO already includes two external validators for ODF and OOXML, so it would be nice to have additional unit tests for PDF/A and use VeraPDF to check for conformance. This way it would be much easier to write a unit test for PDF/A bugs like bug 136805.
Moving to NEW