Careeroza

Accessing and Changing Elements

Index Access

Example

Use [index] to read or write. Indexes start at 0, and the last index is size - 1.

fun main() {
    val scores = arrayOf(72, 88, 95, 60)
    println(scores[0])
    println(scores[scores.size - 1])
    println(scores.last())

    scores[3] = 65              // the array is val, but its elements can change
    println(scores.contentToString())

    println(scores.getOrNull(10))       // safe access
    println(scores.getOrElse(10) { -1 })
}

Output

72
60
60
[72, 88, 95, 65]
null
-1

Index Out of Bounds

Crash

Reading outside the array throws ArrayIndexOutOfBoundsException.

fun main() {
    val days = arrayOf("Mon", "Tue", "Wed")
    println(days[2])
    println(days[3])
}

Output

Wed
Exception: java.lang.ArrayIndexOutOfBoundsException: Index 3 out of bounds for length 3

Looping Over an Array

Example

Loop over the values, the indices, or both.

fun main() {
    val steps = arrayOf(4200, 8100, 10500, 6700)
    for (s in steps) print("$s ")
    println()
    for (i in steps.indices) println("Day ${i + 1}: ${steps[i]}")
    for ((i, s) in steps.withIndex()) if (s >= 10_000) println("Goal reached on day ${i + 1}")
}

Output

4200 8100 10500 6700 
Day 1: 4200
Day 2: 8100
Day 3: 10500
Day 4: 6700
Goal reached on day 3