Problem unzipping with java.util.zip APIs

This isn't post on how to actually use the APIs. What I was wondering if anyone else out there has encounterd compatibility problems with unzipping utilities based on java.util.zip and commercial archiving apps, like Winzip or /n Software's IPWorks! Zip.

I've written a small app that just unzips zip files that are sent to us via ftp. The unzipping part uses the java.util.zip APIs to do the real work. The problem is that one of our clients uses IPWorks! Zip and the app I wrote chokes whenever it tries to unzip their files.

I've been doing some research on zlib version IPWorks is based on and the version that Java uses, but it seems they are based on the same spec. (zlib spec defined in RFC 1950 and deflate spec defined in RFC 1951). At least, after looking at /n Software's site, that's what I gathered. When checking out Winzip's site I found that they may adhere to some later version of zip file format spec.

So, has anyone run into this, and if so what did you find out? Are the java.util.zip APIs based on out-dated specs? Any info much appriciated.

Rich