There’s probably no completely painless way to deal programmatically with the tangled mess of syndication formats, but the Rome project is looking promising. Unlike the Jakarta Commons FeedParser, Rome not only parses feeds but also provides:

• RSS-specific, Atom-specific, and generalized object models–handy if you want to persist feeds after you’ve parsed them;
• generators for all syndication formats;
• conversion from any format to any other.

Apparently, there’s some co-operation brewing between the FeedParser and Rome folks, which will no doubt be good news for Java feed hackers everywhere.