Kotlin setOf

In this guide, we will learn about the Kotlin setOf function with lot's of examples.

What is setOf()? 

The setOf() is a function in Kotlin’s standard library designed to create an immutable (read-only) set. A set is a collection that doesn't allow duplicate elements. Being immutable means that once a set is created using setOf(), its elements cannot be modified - you can't add or remove items. 

Basic Syntax:

val set: Set<Type> = setOf(element1, element2, element3, ...)

Examples with Outputs

Creating a Basic Set

val colors = setOf("Red", "Blue", "Green")
println(colors)  // Output: [Red, Blue, Green]

Uniqueness in Sets 

Sets inherently ensure the uniqueness of elements:

val numbers = setOf(1, 2, 3, 2, 1)
println(numbers)  // Output: [1, 2, 3]

Merging Two Sets 

Merging is simple and retains unique elements:

val set1 = setOf(1, 2, 3)
val set2 = setOf(3, 4, 5)
val mergedSet = set1 + set2
println(mergedSet)  // Output: [1, 2, 3, 4, 5]

Empty and Nullable Sets

val emptySet = setOf<String>()
println(emptySet)  // Output: []

val nullableSet = setOf(null, "Hello")
println(nullableSet)  // Output: [null, Hello]

Convert a Set to a List

val numSet = setOf(1, 2, 3)
val numList = numSet.toList()


Kotlin's setOf() provides a concise and idiomatic way to define immutable sets. In this guide, we went through the usage of the setOf() method with lots of examples.

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