In this guide, we will learn about the Kotlin mapOf() function with lots of examples.

What is mapOf()?

mapOf() is a Kotlin standard library function that's employed to create an immutable map. A map is essentially a collection of key-value pairs. Once created using mapOf(), the map cannot be modified - meaning no new entries can be added, and existing entries can't be removed or altered.

Basic Syntax:

val map: Map<KeyType, ValueType> = mapOf(key1 to value1, key2 to value2, ...)

Engaging Examples with Outputs

Creating a Basic Map

val capitalCities = mapOf("France" to "Paris", "Germany" to "Berlin", "Japan" to "Tokyo")
println(capitalCities)  // Output: {France=Paris, Germany=Berlin, Japan=Tokyo}

Accessing Values Using Keys

val fruits = mapOf("a" to "Apple", "b" to "Banana", "c" to "Cherry")
println(fruits["b"])  // Output: Banana

Using Different Data Types for Keys and Values

val data = mapOf(1 to "one", 2 to "two", 3 to "three")
println(data[2])  // Output: two

Empty Map Creation

val emptyMap = mapOf<String, Int>()
println(emptyMap)  // Output: {}

Map with Nullable Values

val scores = mapOf("Alice" to 90, "Bob" to null, "Charlie" to 85)
println(scores["Bob"])  // Output: null

Getting the Size of a Map

val animals = mapOf(1 to "Dog", 2 to "Cat", 3 to "Bird")
println(animals.size)  // Output: 3

Check if a Map contains a specific key or value

Use the containsKey and containsValue functions:

val colors = mapOf("r" to "Red", "g" to "Green", "b" to "Blue")
println(colors.containsKey("g"))  // Output: true
println(colors.containsValue("Purple"))  // Output: false

Convert an immutable Map to a mutable one

val immutableMap = mapOf(1 to "A", 2 to "B")
val mutableVersion = immutableMap.toMutableMap()

Conclusion

In this guide, we understood how to create an immutable Map in Kotlin using mapOf() function. We also saw different operations of Map with examples.

Java Guides

Search This Blog

Kotlin mapOf