Updating library for Jar/Programs

I'm looking for an update library for the software I am developing. It's a small software, but I'd like to imbue it with some nice features. One of those is auto-update. I've developed 2 class library to do this job for me, but I'd like a more robust library, becuase it's missing some features. Between the features the library could have, these could be in it: - Generate a difference file based on the old version (jar for example). Given the current version of the jar, and the new jar file, generate a new jar that will be downloaded by the clients, puting only the files that were changed since the last update. - Check some kind of checksum. Each file inside the JAR have it's own checksum, or the whole jar having a checksum. - Generate those checksum. If possible, while attending to the first item. File by file, or jar by jar, given the new files. - It would be nice if it could deal also if the input is a folder or a jar. - Merge the current jar with the downloaded one. P.S.: I'm not writing a web-based (that runs in a browser) application. Thanks for the attention.