Is it allowed for a `public class` to implement an `internal interface`?

# getting-started

[Lukasz Kalnik]

Is it allowed for a public class to implement an internal interface?

[Lukasz Kalnik]

Ok, then I have some caching issue in my Android Studio because it doesn't show it as error...

[Lukasz Kalnik]

image.png

[Lukasz Kalnik]

I don't get a compile error somehow

[Lukasz Kalnik]

Android Studio Giraffe (Canary)

[mankin]

That is not an error, it's a warning. It's saying that the MyClass is never used elsewhere.

Either use it somewhere or add @Suppress("UNUSED") on top of the class.

Note: the warning can be there for a good reason, suppressing it only makes sense for libraries and you do not want to add test for that class.

[Lukasz Kalnik]

The screenshot referred to my original question: MyClass should be underscored squiggly red, as it is a public class which extends an internal interface.

[Lukasz Kalnik]

This should not compile

[mankin]

internal just means it's not visible outside the current module/project, if it's in the same module/project it's compile fine I would say (it might fail if you return/expose the interface as a type in some method)

[Lukasz Kalnik]

I would think that you should not be able even to create such class, as a public class would then be able to expose an internal interface to outside code

[mankin]

That's the whole point, you do not expose the interface (it's members) outside your module.

https://discuss.kotlinlang.org/t/what-is-the-purpose-of-an-internal-interface/25384/12

[Lukasz Kalnik]

Ah, so the methods of an internal interface are still publicly visible...

[Lukasz Kalnik]

Thank you for the helpful link!