How to parse large files using flatpack

I need to parse files that may be quite large, possibly 100s of megabytes and millions of lines. I have been trying to do this using FlatPack. I would think the way to do this would be to use the buffered parsers and the new stream methods. But, despite that dataset.next() returns true for the correct number of records, the Optional returned by dataset.getRecord() never contains a value.

I have looked at this example/test but it only counts the number of record and does not actually do anything with the content. example/test