Consider this, the only reason anyone would really need a web-based version is so they can check on their mobile devices (Since your java application can be used on virtually any desktop platform). Since it's java based, it would be extremely easy to make an android application out of it, you would just need to redo the layout a bit and deal with a tiny bit of android api. You could do similarly with iOS, I'm sure there is a converter of sorts for it. (But you'll still need a mac computer to compile the xcode project or whatever else it does, just to comply with the apple store even).
You would want to charge extra for the iOS version since you actually need to pay for a license to post apps on the app store.