2D Array in Kotlin

Question

How do you make a 2D Int array in Kotlin? I'm trying to convert this code to Kotlin:

int[][] states = new int[][] {
      new int[]{-android.R.attr.state_pressed}, // not pressed
      new int[] { android.R.attr.state_pressed}  // pressed
};
int[] colors = new int[] {
      foregroundColor,
      accentColor,
      accentColor
};
ColorStateList myList = new ColorStateList(states, colors);

Here is one attempt I tried, where the first 2D array didn't work, but I got the 1D array to work:

//This doesn't work:
var states: IntArray = intArrayOf(
    intArrayOf(-android.R.attr.state_pressed), // not pressed
    intArrayOf(android.R.attr.state_pressed)  // pressed
);
//This array works:
var colors: IntArray = intArrayOf(
    foregroundColor,
    accentColor,
    accentColor
);
val myList: ColorStateList = ColorStateList(states, colors);

score 118 · Answer 1 · edited Jun 30 '20 at 04:06

118

You may use this line of code for an Integer array.

val array = Array(row) { IntArray(column) }

This line of code is pretty simple and works like 1D array and also can be accessible like java 2D array.

edited Jun 30 '20 at 04:06

Animesh Sahu

7,445
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answered Jun 10 '17 at 09:45

HM Nayem

2,287
1
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10

1

This work well and just to add here if you want to create a 2D array with nulls you can use that -> val array = Array(row) { arrayOfNulls(column) } – MrVasilev Jun 08 '22 at 07:16
1

Here `row` and `column` are the number of rows and number of columns in your 2D array. – Codextor Jun 18 '22 at 22:46

score 79 · Accepted Answer · answered Dec 08 '15 at 00:01

79

You are trying to put your IntArrays inside another array to make it 2-dimensional. The type of that array cannot be intArray, which is why this fails. Wrap your initial arrays with arrayOf instead of intArrayOf.

val even: IntArray = intArrayOf(2, 4, 6)
val odd: IntArray = intArrayOf(1, 3, 5)

val lala: Array<IntArray> = arrayOf(even, odd)

answered Dec 08 '15 at 00:01

Tim

958
7
8

2

I'm basically creating n 1d arrays and appending those into another array to make a 2d array? – Cyril Sep 25 '18 at 17:01

A-Sharabiani · Answer 3 · 2019-02-27T02:11:54.720

49

Short Answer:

// A 6x5 array of Int, all set to 0.
var m = Array(6) {Array(5) {0} }

Here is another example with more details on what is going on:

// a 6x5 Int array initialise all to 0
var m = Array(6, {i -> Array(5, {j -> 0})})

The first parameter is the size, the second lambda method is for initialisation.

edited Feb 27 '19 at 02:11

answered Feb 27 '19 at 02:03

A-Sharabiani

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What about unlimited size? – Thanasis Jan 16 '20 at 16:07
1

how i insert data this? i try m[0][0]= – tedris Feb 08 '20 at 14:51
1

Thank you! Such a simple problem took waaaay too much time. Perfect. I'll be using this from now on. – Alex.Gunning May 12 '20 at 21:27

score 28 · Answer 4 · answered May 05 '19 at 20:50

28

I have been using this one-liner when creating matrix

var matrix: Array<IntArray> = Array(height) { IntArray(width) }

answered May 05 '19 at 20:50

pajus_cz

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s1m0nw1 · Answer 5 · 2019-04-01T11:59:15.753

1. Nested arrayOf calls

You can nest calls of arrayOf, e.g., to create an Array of IntArray, do the following:

val first: Array<IntArray> = arrayOf(
    intArrayOf(2, 4, 6),
    intArrayOf(1, 3, 5)
)

Note that the IntArray itself only takes arguments of type Int as arguments, so you cannot have an IntArray<IntArray> which obviously does not make much sense anyway.

2. Use Array::constructor(size: Int, init: (Int) -> T) for repeated logic

If you want to create your inner arrays with some logical behaviour based on the index, you can make use of the Array constructor taking a size and an init block:

val second: Array<IntArray> = Array(3) {
    intArrayOf(it * 1, it * 2, it * 3, it * 4)
} 
//[[0, 0, 0, 0], [1, 2, 3, 4], [2, 4, 6, 8]]

voghDev · Answer 6 · 2020-01-30T08:13:42.103

6

It seems that you are trying to create a ColorStateList in Kotlin. The code for that is a bit messy, i'll try to keep it readable:

val resolvedColor = Color.rgb(214, 0, 0)
val states = arrayOf(
    intArrayOf(-android.R.attr.state_pressed),
    intArrayOf(android.R.attr.state_pressed)
)

val csl = ColorStateList(
    states,
    intArrayOf(resolvedColor, Color.WHITE)
)

edited Jan 30 '20 at 08:13

answered Oct 03 '17 at 06:38

voghDev

5,641
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score 3 · Answer 7 · answered Jan 31 '19 at 06:17

You can use a simple 1D (linear) array for this purpose. For example, this is my class for a rectangle array of Double values:

/**
 * Rect array of Double values
 */
class DoubleRectArray(private val rows: Int, private val cols: Int) {
    private val innerArray: DoubleArray

    init {
        if(rows < 1) {
            throw IllegalArgumentException("Rows value is invalid. It must be greater than 0")
        }

        if(cols < 1) {
            throw IllegalArgumentException("Cols value is invalid. It must be greater than 0")
        }

        innerArray = DoubleArray(rows*cols)
    }

    /**
     *
     */
    fun get(row: Int, col: Int): Double {
        checkRowAndCol(row, col)
        return innerArray[row*cols + col]
    }

    /**
     *
     */
    fun set(row: Int, col: Int, value: Double) {
        checkRowAndCol(row, col)
        innerArray[row*cols + col] = value
    }

    /**
     *
     */
    private fun checkRowAndCol(row: Int, col: Int) {
        if(row !in 0 until rows) {
            throw ArrayIndexOutOfBoundsException("Row value is invalid. It must be in a 0..${rows-1} interval (inclusive)")
        }

        if(col !in 0 until cols) {
            throw ArrayIndexOutOfBoundsException("Col value is invalid. It must be in a 0..${cols-1} interval (inclusive)")
        }
    }
}

Sad but true, this seems to be the only reasonable way to handle 2D arrays in Kotlin and I cannot even find this in the standard library. My feeling is to advise anyone against using Kotlin for data science, scientific computing, statistics, machine learning etc. — ChrisoLosoph, Jul 27 '23 at 02:28

score 2 · Answer 8 · edited Oct 18 '20 at 07:27

package helloWorld

import java.util.Scanner

fun main(){
    val sc = Scanner(System.`in`)
    print("ENTER THE SIZE OF THE ROW: ")
    var row = sc.nextInt()
    println()
    print("ENTER THE SIZE OF COLUMN: ")
    val column = sc.nextInt()
    println()
    var a = Array(row){IntArray(column)}
    for(i in 0 until row){
        when (i) {
            0 -> {
                println("----------${i+1} st ROW'S DATA----------")
            }
            1 -> {
                println("----------${i+1} nd ROW'S DATA----------")
            }
            2 -> {
                println("----------${i+1} rd ROW'S DATA----------")
            }
            else -> {
                println("----------${i+1} th ROW'S DATA----------")
            }
        }
        for(j in 0 until column)
        {
            print("ENTER ${j+1} COLUMN'S DATA: ")
            var data:Int = sc.nextInt()
            a[i][j]=data;
        }
        println()
    }
    println("COLLECTION OF DATA IS COMPLETED")
    for(i in 0 until row){
        for(j in 0 until column){
            print(a[i][j])
            print(" ")
        }
        println()
    }


}

It works like this:

score 2 · Answer 9 · answered Mar 07 '22 at 15:48

2

You can create 2D array in kotlin.

            var twoDarray = Array(8) { IntArray(8) }

this is a example of int 2D array

answered Mar 07 '22 at 15:48

Adarsh Dhakad

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jnfran92 · Answer 10 · 2020-02-20T18:27:50.940

Using an inline function and a Pair:

  inline fun<reified T> Pair<Int,Int>.createArray(initialValue:T) = Array(this.first){ Array(this.second){initialValue}}

  // Create m*n Array of Ints filled with 0
  val twoDimArray = Pair(10,20).createArray(0)

  // Create m*n Array of Doubles filled with 0.0
  val twoDimArray = Pair(10,20).createArray(0.0)

  // Create m*n Array of Strings filled with "Value"
  val twoDimArray = Pair(10,20).createArray("Value")

  ...

score 0 · Answer 11 · answered Jul 14 '19 at 12:36

You can create two one dimensional array and add them in new array.

val unChecked = intArrayOf(-android.R.attr.state_checked)
val checked = intArrayOf(android.R.attr.state_checked)
val states = arrayOf(unChecked, checked)

val thumbColors = intArrayOf(Color.WHITE, Color.parseColor("#55FFD4"))
val stateList = ColorStateList(states, thumbColors)

2D Array in Kotlin

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