I can apparently find one old implementation of xdelta in java: https://sourceforge.net/projects/javaxdelta/ which has then been reused and possibly improved in https://github.com/mantlik/xdeltaencoder. Now those are using GDIFF format for the patch it seems, and it's unmaintained/unreleased projects.
We could maybe ask if that's something that would be interesting to have in https://github.com/java-diff-utils/java-diff-utils: right now the repo is really focused on text diff, but since the repo is "java-diff-utils" it might be interesting to also have other kind of diffs.