How to construct java sealed class in kotlin? It's...

# getting-started

[Settingdust]

How to construct java sealed class in kotlin? It's will Sealed types cannot be instantiated when try to init

[Michael de Kaste]

You cannot instantiate a sealed class much less that you can instantiate an enum without a value. There is no such thing as 'just' a 'Planet class' in the enum planet { EARTH, MARS, etc. }

[Ronny Bräunlich]

What do you want to achieve? A sealed hierarchy or a class that cannot be subclassed?

[Settingdust]

I can init java sealed class in java but not in kotlin. It's "Java Sealed Class" instead of kotlin one

[xoangon]

The Java equivalent Kotlin sealed class is an abstract class. You can't instantiate a sealed class for the same reason you cab't instantiate an abstract class

[Daniel Pitts]

What is a java sealed class?

[Daniel Pitts]

Ah, new in Java 15.

[Daniel Pitts]

I see. Kotlin assumes sealed classes are always abstract, so can't be instantiated, where Java doesn't have such a limitation.

[Daniel Pitts]

So, in Java, you can instantiate the base class if it isn't abstract, but in Kotlin you can't.

[Daniel Pitts]

You can get around this by creating a utility method in Java that does the instantiation, but it appears you can't do it in pure Kotlin.

[Daniel Pitts]

sealed class Foo permits Bar {
    static @NotNull Foo instance() {
        return new Foo();
    }
}

Then in Kotlin, you can call Foo.instance()