Well, the API in question (which I've used, and it was indeed an unpleasant experience) might not be solving something trivial, but it's certainly not well designed.

My all-time worse API is SetupAPI, which despite its name is how you get access to USB devices on Windows. It's . . . pretty miserable. Runner-up is the COM-based stuff that manages the Windows firewall, which is not well specified and has 'interesting' timing issues.

I have mercifully lost most of my memory of the Java stuff I was doing 15 years ago. That stuff made me hate life.