It’s difficult in the sense that somebody consuming your class will sooner or later start relying on reflection to do something with it they shouldn’t (because

It’s difficult in the sense that somebody consuming your class will sooner or later start relying on reflection to do something with it they shouldn’t (because they can), and then when you make a change in the future it will cause breakage downstream. Records solved this for some cases at least. More important imo is that the standard collection classes can’t even be set to immutable with the final keyword. Sure you can use something else, but professionally you are going to have to deal with them most of the time still.