Sealed Hierarchies: Introduction

An introduction to sealed classes and sealed interfaces, also called sum or union types, and a teaser for what they’re actually good for.

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THE CURRENT VERSION OF THIS ARTICLE IS PUBLISHED HERE.

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Tags: #KOTLIN FEATURE

This article is part of the Kotlin Primer, an opinionated guide to the Kotlin language, which is indented to help facilitate Kotlin adoption inside Java-centric organizations. It was originally written as an organizational learning resource for Etnetera a.s. and I would like to express my sincere gratitude for their support.

It is recommended to read the Introduction before moving on. Check out the Table of Contents for all articles.

Before we start, let me say that I honestly believe that the concepts discussed in the following chapters are among the most important things you can take away from the Primer — concepts which will open up your mind to new ways of designing, even outside of Kotlin, and make you a better programmer, period.