Is it possible to run a Java program on iOS?
If so, what technologies should I use?
It is possible to develop an application with JavaFX and I would like to run it on iOS, is it possible? instead on Android, do I have to make any particular changes?
You can do that via the tools from https://gluonhq.com/products/mobile/ The code for Android and iOS is mostly identical. This tutorial https://foojay.io/today/creating-mobile-apps-with-javafx-part-1/ may get you started.