Comment by weksf54

Ah! Thanks, I didn't know that. I should have RTFMD better - https://docs.oracle.com/en/java/javase/21/language/sealed-cl...

Turns out you can do this and not have the annoying inner class e.g. Vehicle.Car too:

  package com.example.vehicles;

  public sealed interface Vehicle
      // The permits clause has been omitted
      // as its permitted classes have been
      // defined in the same file.
  { }
  record Truck(int loadCapacity) implements Vehicle {}
  record Car(int numberOfSeats, String brandName) implements Vehicle {}