List access

Learn list access with get, indexOf and subList.

List access: get, indexOf, subList

There are several ways to reach a list element. get(i) (or [i]) returns the element at index i. indexOf(x) gives the first index where x appears, or -1 if not found. subList(from, to) returns the range [from, to) as a new list.

val fruits = listOf("apple", "banana", "cherry", "grape")
fruits.get(0)              // "apple"
fruits.indexOf("banana")  // 1
fruits.subList(1, 3)       // [banana, cherry]

Indexes start at 0 and end at size - 1. The end of the range (to) is exclusive; that is why subList(1, 3) takes indexes 1 and 2.

The range of subList: [from, to)

subList(from, to) includes index from and excludes index to. So subList(1, 3) gives indexes 1 and 2; index 3 is not included.

val f = listOf("a", "b", "c", "d", "e")
val middle = f.subList(1, 4)  // [b, c, d]

This half-open range matches Kotlin's 1..4 (closed) and 1 until 4 (open) ranges. It makes index math easier.

Exercise Print the first fruit, the index and the slice

Create a listOf("apple", "banana", "cherry", "grape"). Use get(0) to assign the first fruit to first, indexOf("banana") for the index i, and subList(1, 3) for the slice. Print each on its own line with println.

Show example solution

fun main() {
    val fruits = listOf("apple", "banana", "cherry", "grape")
    val first = fruits.get(0)
    val i = fruits.indexOf("banana")
    println(first)
    println(i)
    println(fruits.subList(1, 3))
}

Test yourself

Match access expression to result

get(0)

First element
indexOf(x)

Position of x (-1 if missing)
subList(1, 3)

Indexes 1 and 2
size - 1

Last index
What does list.indexOf("missing") return?
- 0
- Throws an exception
- null
- -1
Show answer

-1 — indexOf returns -1 when not found; no null, no exception.

Fill in the blank: get the first element

val first = fruits.____(0)

Show answer

val first = fruits.get(0)

Next lesson: List iteration

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