Array declaration in Kotlin

Question

The code below is an example for Array declaration in Kotlin,

fun main(args: Array<String>) {

    var a = Array<Int>(2){0}
    a[0] = 100
    a[1] = 200
    print(a[1])

}

Here variable a is an array of size 2 and having values 100 and 200 and it is printing the value of a[1] as 200.

My question is -> What is the role of "0" in var a = Array(2){0}?

I changed the value of "0" to some other integer value, still it is working fine, but i was not able to find the use case of it. Can anyone explain it?

Any help will be appreciated.

Thanks.

Using Array<Int> involves autoboxing. For performance you should use IntArray. But I know this is a simple example. — user221256
– user221256, Commented May 9, 2018 at 12:55
I was just started studying Kotlin, thanks for the suggestion. — Sachin Varma
– Sachin Varma, Commented May 9, 2018 at 12:57

s1m0nw1 · Accepted Answer · 2018-05-09 16:23:18Z

6

The 0 is what you initialize each element of your array (2 in your case) with, using the following constructor:

public inline constructor(size: Int, init: (Int) -> T)

You can make this visible by printing the array directly after its initialization:

var a = Array<Int>(2){0}
println(a.contentToString())

Please consider the use of arrayOf(0,0) for such a simple use case, which is more idiomatic.

edited May 9, 2018 at 16:23

answered May 9, 2018 at 10:38

s1m0nw1

83k17 gold badges181 silver badges200 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Sachin Varma Over a year ago

got answer as [Ljava.lang.Integer;@28a418fc while printing a.

s1m0nw1 Over a year ago

sorry, review my edit please: println(a.contentToString())

IntelliJ Amiya · Accepted Answer · 2018-05-09 10:43:24Z

3

Arrays in Kotlin are represented by the Array class, that has get and set functions (that turn into [] by operator overloading conventions), and size property, along with a few other useful member functions:

class Array<T> private constructor() {
    val size: Int
    operator fun get(index: Int): T
    operator fun set(index: Int, value: T): Unit

    operator fun iterator(): Iterator<T>
    // ...
}

You can write

var a = Array(2){0}

Creates a new array with 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) -> T)

Read Arrays in Kotlin.

edited May 9, 2018 at 10:43

answered May 9, 2018 at 10:37

IntelliJ Amiya

75.8k15 gold badges169 silver badges199 bronze badges

1 Comment

Sachin Varma Over a year ago

Thanks for the answer.

Collectives™ on Stack Overflow

Array declaration in Kotlin

2 Answers 2

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related