JuniorTheoryCommon

What does the program print?

KOTLIN

fun main() {
    val items = mutableListOf(1, 2)
    val view: List<Int> = items
    items.add(3)
    println(view)
}

[1, 2, 3]

Expecting [1, 2]: giving a list a List name copies nothing. view and items name one list, so view sees the 3 added through items.
Expecting val to forbid add: val only stops items from naming another list; the list itself can still grow with add.

JuniorTheoryCommon

KOTLIN

fun main() {
    val items = mutableListOf(1, 2)
    val view: List<Int> = items
    items.add(3)
    println(view)
}

[1, 2, 3]

Expecting [1, 2]: giving a list a List name copies nothing. view and items name one list, so view sees the 3 added through items.
Expecting val to forbid add: val only stops items from naming another list; the list itself can still grow with add.