Been coding Java for about 15 years now. Pretty much agree - anon’s primary mistake was using javaFX. From a junior dev perspective I can see why they’d do that, but Java isn’t really meant for building desktop applications, it’s meant to power web apps.

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. Java has some awesome frameworks built for it over the years, something like spring boot would make building that backend service trivial if you know how to use it. JAX-RS/Jersey or even servlets could be utilized for this instead, if you wanted to.

Spring boot has some nice tooling for thread management, but Java also has pretty good options for this built in as well. As chunky mentioned, if you aren’t already versed in concurrency patterns, don’t try to perform concurrent operations or you’re gonna have a bad time. But do learn how to do this, because exploiting concurrency is one of the golden rules of good computing.