How to add an item to an ArrayList in Kotlin?

Question

How to add an item to an ArrayList in Kotlin?

Answer 1

If you have a MUTABLE collection:

val list = mutableListOf(1, 2, 3)
list += 4

If you have an IMMUTABLE collection:

var list = listOf(1, 2, 3)
list += 4

note that I use val for the mutable list to emphasize that the object is always the same, but its content changes.

In case of the immutable list, you have to make it var. A new object is created by the += operator with the additional value.