Kotlin Kotlin Collections and Generics

Question 1

Which Kotlin collection is immutable by default?

Accepted Answer

List

Answer

ArrayList

Answer

MutableList

Answer

LinkedList

Question 2

How do you create a mutable list in Kotlin?

Accepted Answer

mutableListOf()

Answer

listOf()

Answer

arrayListOf() only

Answer

MutableList()

Question 3

What does the `groupBy` function do in Kotlin?

Accepted Answer

Groups elements into a map by a key selector function

Answer

Sorts elements into groups by value

Answer

Removes duplicate elements

Answer

Partitions elements into two lists

Question 4

Which function returns the first element matching a predicate or null in Kotlin?

Accepted Answer

find()

Answer

first()

Answer

filter()

Answer

get()

Question 5

What does `flatMap` do in Kotlin?

Accepted Answer

Maps each element and then flattens the resulting nested collections

Answer

Flattens a list of lists into one list

Answer

Converts a map to a flat list

Answer

Sorts and flattens a collection

Question 6

What is `Pair` in Kotlin?

Accepted Answer

A data class holding two values of potentially different types

Answer

A mutable two-element list

Answer

A map with two entries

Answer

A tuple with two comparable values