# Sealed classes and interfaces in Kotlin

DevFeed: [Sealed classes and interfaces in Kotlin](<https://devfeed.tech/articles/sealed-classes-and-interfaces-in-kotlin-39339.md>)

Original publisher: [Read original article](<https://kt.academy/article/kfde-sealed>)

Published: 2023-09-04T00:01:00Z

Content type: tutorial

Language: en

Sources: [Kt. Academy](<https://devfeed.tech/sources/kt-academy.md>)

Topics: [Kotlin](<https://devfeed.tech/topics/kotlin.md>), [sealed class](<https://devfeed.tech/topics/sealed-class.md>), [sealed interface](<https://devfeed.tech/topics/sealed-interface.md>), [interface](<https://devfeed.tech/topics/interface.md>), [abstract class](<https://devfeed.tech/topics/abstract-class.md>), [Inheritance](<https://devfeed.tech/topics/inheritance.md>), [Polymorphism](<https://devfeed.tech/topics/polymorphism.md>)

Tags: [inheritance](<https://devfeed.tech/tags/inheritance.md>), [interface](<https://devfeed.tech/tags/interface.md>), [kotlin](<https://devfeed.tech/tags/kotlin.md>), [polymorphism](<https://devfeed.tech/tags/polymorphism.md>), [sealed](<https://devfeed.tech/tags/sealed.md>), [sealed-classes](<https://devfeed.tech/tags/sealed-classes.md>), [sealed-interface](<https://devfeed.tech/tags/sealed-interface.md>), [workshop-learning-programming](<https://devfeed.tech/tags/workshop-learning-programming.md>)

## AI overview

This Kotlin tutorial explains sealed classes and sealed interfaces as restricted hierarchies whose direct subclasses are controlled. It contrasts them with regular interfaces and abstract classes, describes their package and module requirements, and explains their use in exhaustive expressions.

## Source excerpt

What are sealed classes and interfaces in Kotlin and how do we use them.