Creating arrays

Learn to create arrays with arrayOf and intArrayOf.

Creating arrays

An array is a fixed-size collection. In Kotlin, arrayOf creates an array of any type.

val fruits = arrayOf("apple", "pear", "cherry")
val nums = intArrayOf(3, 7, 2, 5)
println(fruits.contentToString())  // [apple, pear, cherry]

arrayOf makes a general array (Array<String>). intArrayOf makes a specialized array for Ints (IntArray); it uses less memory.

To print an array's contents, use contentToString(); plain println(array) prints an address. Array size does not change after creation.

Array and IntArray

arrayOf and intArrayOf produce different types. arrayOf(1, 2, 3) gives an Array<Int>; intArrayOf(1, 2, 3) gives an IntArray.

val a = arrayOf(1, 2, 3)       // Array<Int>
val b = intArrayOf(1, 2, 3)    // IntArray
println(a[0])  // 1
println(b[0])  // 1

Both use the same access syntax: array[index]. IntArray is primitive-based; it is more efficient for large amounts of numbers.

arrayOf is for complex types (String, objects); intArrayOf is for Ints only.

Exercise Create an array and print it

Write a fun main(). Create an array with val fruits = arrayOf("apple", "pear", "cherry"). Print its contents with println(fruits.contentToString()).

Show example solution

fun main() {
    val fruits = arrayOf("apple", "pear", "cherry")
    println(fruits.contentToString())
}

Test yourself

What type of array does arrayOf("a", "b", "c") create?
- List<String>
- IntArray
- String
- Array<String>
Show answer

Array<String> — arrayOf creates an Array<String> of Strings.

Complete the arrayOf call

val fruits = ____("apple", "pear", "cherry")

Show answer

val fruits = arrayOf("apple", "pear", "cherry")

Match the array creation forms

arrayOf(...)

General array
intArrayOf(...)

Int array
Array<String>

String array type
IntArray

Int array type

Next lesson: Array access

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