Hello,
This project is currently under development but it basically works at the moment:
https://github.com/fge/java7-fs-dropbox
This means you can use the Files class to manipulate your dropbox repositories!
Ie, if a path "src" is on your local filesystem and "dst" is on DropBox, you can do:
Files.copy(src, dst);
And it will work! Of course, the reverse works too.
Note that metadata support is VERY limited... I'm open to ideas on how to improve upon that, of course!