Derby is/was the other alternative for an in JVM database.

For a long time, it was possible/practical to use SQLite from Java. Now, it is, but not if you want to keep things as pure Java (and another commenter mentioned). But really, in my mind, that’s the only real benefit for H2, the fact that’s it’s pure Java. So if you need that, you’re good.

But otherwise, I try to stick to SQLite.