Thanks all for your comments, Yes, the package will be different for date or time stamps reason and comparing hashes (MD5 or SHA1) seems to be not enough. But it's not always a problem to have such differences and it would be nice to find a tools that shows what changes from two packages.
I had a look to JarDiff (http://www.osjava.org/jardiff/) but it's just for jar packaging and for java classes. Regards, Rémy
