How to initialize an array in Kotlin with values?

Question

In Java an array can be initialized such as:

int numbers[] = new int[] {10, 20, 30, 40, 50}

How does Kotlin\'s array initialization look li

Answer 1

Old question, but if you'd like to use a range:

var numbers: IntArray = IntRange(10, 50).step(10).toList().toIntArray()

Yields nearly the same result as:

var numbers = Array(5, { i -> i*10 + 10 })

result: 10, 20, 30, 40, 50

I think the first option is a little more readable. Both work.

Answer 2

You can simply use the existing standard library methods as shown here:

val numbers = intArrayOf(10, 20, 30, 40, 50)

It might make sense to use a special constructor though:

val numbers2 = IntArray(5) { (it + 1) * 10 }

You pass a size and a lambda that describes how to init the values. Here's the documentation:

/**
 * Creates a new array of the specified [size], where each element is calculated by calling the specified
 * [init] function. The [init] function returns an array element given its index.
 */
public inline constructor(size: Int, init: (Int) -> Int)

Answer 3

Worth mentioning that when using kotlin builtines (e.g. intArrayOf(), longArrayOf(), arrayOf(), etc) you are not able to initialize the array with default values (or all values to desired value) for a given size, instead you need to do initialize via calling according to class constructor.

// Array of integers of a size of N
val arr = IntArray(N)

// Array of integers of a size of N initialized with a default value of 2
val arr = IntArray(N) { i -> 2 }

Answer 4

In Kotlin There are Several Ways.

var arr = IntArray(size) // construct with only size

Then simply initial value from users or from another collection or wherever you want.

var arr = IntArray(size){0}  // construct with size and fill array with 0
var arr = IntArray(size){it} // construct with size and fill with its index

We also can create array with built in function like-

var arr = intArrayOf(1, 2, 3, 4, 5) // create an array with 5 values

Another way

var arr = Array(size){0} // it will create an integer array
var arr = Array<String>(size){"$it"} // this will create array with "0", "1", "2" and so on.

You also can use doubleArrayOf() or DoubleArray() or any primitive type instead of Int.

Answer 5

In Java an array can be initialized such as:

int numbers[] = new int[] {10, 20, 30, 40, 50}

But In Kotlin an array initialized many way such as:

Any generic type of array you can use arrayOf() function :

val arr = arrayOf(10, 20, 30, 40, 50)

val genericArray = arrayOf(10, "Stack", 30.00, 40, "Fifty")

Using utility functions of Kotlin an array can be initialized

val intArray = intArrayOf(10, 20, 30, 40, 50)

Answer 6

intialize array in this way : val paramValueList : Array<String?> = arrayOfNulls<String>(5)