Hello, I'm modeling the different types of audio focus as a Kotlin type hierarchy, and I'm unsure about picking

sealed interface

or

sealed class

. What would you pick? Any reason beyond personal preference? 1️⃣ Here's with `interface`:

sealed interface AudioFocus {
    object Gain : AudioFocus
    sealed interface Loss : AudioFocus {
        companion object : Loss
        sealed interface Transient : Loss {
            companion object : Transient
            object CanDuck : Transient
        }
    }
}

2️⃣ Here's with `class`:

sealed class AudioFocus {
    object Gain : AudioFocus()
    sealed class Loss : AudioFocus() {
        companion object : Loss()
        sealed class Transient : Loss() {
            companion object : Transient()
            object CanDuck : Transient()
        }
    }
}

If an interface can be used, I would use it, if you need local variables with backing fields, I would use a class

sealed interfaces don't protect you from instantiation in Java, so at least until support for JEP 360 lands, I'd use sealed classes except when interfaces are required (multiple hierarchies, enums)

1 if you’re only targeting kotlin consumers, 2 if you are worried about java consumers

something like this, with a DAG-like set of hierarchies instead of a single tree-like hierarchy, is only doable with

interface

Thanks for sharing your thoughts! I settled with

sealed interface

(Java compatibility isn't a concern in my case). Here's a full gist that includes a suspend-first API to work with AudioFocus on all Android versions: https://gist.github.com/LouisCAD/4ca4bd6cb85e3d8b2509492d67b282f7