Creating maps

Learn to create maps with mapOf and mutableMapOf.

Creating maps: mapOf and mutableMapOf

A map binds keys to values. mapOf returns a read-only map, while mutableMapOf gives a mutable map. Pairs are written with to: "key" to value.

val ages = mapOf("Ava" to 25, "Liam" to 30)
println(ages["Ava"])  // 25

Keys are unique: if you write the same key twice, the second value overwrites the first. The inferred type looks like Map<String, Int>.

You get all keys of a map with keys, all values with values, and key-value pairs with entries. You can iterate them like a list.

val ages = mapOf("Ava" to 25, "Liam" to 30)
ages.keys      // [Ava, Liam]
ages.values    // [25, 30]
ages.entries   // [Ava=25, Liam=30]

entries returns a set of Entry<K, V>. Each entry has .key and .value fields.

Create a mapOf("Ava" to 25, "Liam" to 30) and print it with println.

Show example solution

fun main() {
    val ages = mapOf("Ava" to 25, "Liam" to 30)
    println(ages)
}

Fill in the blank: read-only map

val ages = ____("Ava" to 25, "Liam" to 30)

Show answer

val ages = mapOf("Ava" to 25, "Liam" to 30)