J2ObjC is a command-line tool that translates Java to Objective-C 5 years ago
J2ObjC does not provide any sort of platform-independent UI toolkit, nor are there any plans to do so in the future. We believe that iOS UI code needs to be written in Objective-C, Objective-C++ or Swift using Apple's iOS SDK (Android UIs using Android's API, web app UIs using GWT, etc.).
Weird statement by the company who created flutter.