In Kotlin Programming language importance of varargs in terms of uses

Question

Let me know what is the importance of varargs in Kotlin, if there is any document or some useful links. Please share.

Answer 1

The vararg parameters allow for functions that accept variable number of arguments in a natural way, i.e. without creating an array or a collection first, filling it with the items, and only then passing it, compare:

_{If there were no vararg parameters:}

val items = ArrayList<String>().apply { add("foo"); add("bar"); add("baz") }
qux(items)

_{With vararg:}

qux("foo", "bar", "baz")

This is particularly useful for initializing collections and other containers, and there are numerous functions for that in kotlin-stdlib, such as arrayOf(...), listOf(...), setOf(...), mapOf(...), sequenceOf(...) and more.

To see the usages in kotlin-stdlib, search for the word 'vararg' in the API reference pages (there's a lot in packages kotlin.collections, kotlin.text).

Basically, if there is a function accepting a collection that a user might frequently call with only a few items (and choose the items right before the call), it makes sense to provide a vararg overload for that function.