Enum vs sealed class — which should I use?

Use enum for simple fixed constants. Use sealed class when variants carry different data or behaviour.

Can enum constants have bodies?

Yes. Each constant can override methods or use anonymous class bodies for custom behaviour.

Beginner 7 min readKotlin 2.0

Kotlin Enum Classes — Named Constants with Power

Enum classes represent a fixed set of constants. Each constant is an object instance of the enum class.

What You Will Learn

Declare enum classes
Add properties and methods to enums
Use enums in when expressions
Iterate enum values with values()
Choose enum vs sealed class

Basic Enum

Use enum class to define a closed set of named values — directions, statuses, days of the week.

Simple Enum

kotlin
enum class Status { ACTIVE, INACTIVE, PENDING }

fun main() {
    val s = Status.ACTIVE
    println(s)
    println(s.name)
}

Output

ACTIVE ACTIVE

Each constant is a singleton instance. name returns the constant identifier as a String.

Enums with Properties

Enum constants can have constructor parameters, turning each constant into a rich object.

Enum with Data

kotlin
enum class Planet(val massKg: Double) {
    EARTH(5.97e24),
    MARS(6.39e23)
}

fun main() {
    for (p in Planet.entries) {
        println("${p.name}: ${p.massKg}")
    }
}

Output

EARTH: 5.97E24 MARS: 6.39E23

Planet.entries (Kotlin 1.9+) lists all constants. Each stores its massKg value.

Practice Exercise

Exercisepredict output

What prints? enum class Color { RED, GREEN } fun main() { println(Color.GREEN.ordinal) }

Quick Quiz

When are enum classes the best choice?