What they should have done instead is create a backend restful web service and wire up a frontend rest client with something suited to web app ui dev such as angular or react.

If anon's program was designed to work as a client for some external server or if Java had absolutely no GUI frameworks, that would be fine. But if anon's goal was to create a simple desktop application, doing this would be the programming equivalent of a Rube Goldberg machine.

With that approach, you also need to be really careful about how you do it. Fuck that part up and you can end up with the locally-hosted REST server listening on the device's public network interface or vulnerable to CSRF from a web page opened in the user's browser.