20. Lists

A List is an ordered collection. listOf returns a read-only List, while mutableListOf gives you one you can modify.

fun main() {
    val colors = listOf("red", "green", "blue")
    println(colors[0])      // index access
    println(colors.first())
    println(colors.last())
    println(colors.size)

    val numbers = mutableListOf(1, 2, 3)
    numbers.add(4)
    numbers.remove(2)
    println(numbers)
}

The List returned by listOf is read-only: it exposes no add or remove, so the contents are stable. Choose mutableListOf only when you genuinely need to change the collection after creation.

Running it:

$ kotlin run
red
red
blue
3
[1, 3, 4]

← Prev

Index

Next →