Kotlin Kotlin Collections 2

Question 1

What does `groupBy` return in Kotlin?

Accepted Answer

A Map where keys are the grouping criteria and values are lists of elements

Answer

`groupBy` returns a `Map>` where each key maps to a list of elements that share that key.

Question 2

Which function finds the first element matching a predicate in Kotlin?

Accepted Answer

firstOrNull

Answer

`firstOrNull` returns the first element matching the predicate, or `null` if no element matches, avoiding a NoSuchElementException.

Question 3

How do you sort a list in descending order in Kotlin?

Accepted Answer

list.sortedDescending()

Answer

`sortedDescending()` returns a new list sorted in descending order without modifying the original list.

Question 4

What does the `any` function do on a Kotlin collection?

Accepted Answer

Returns true if at least one element satisfies the predicate

Answer

`any` returns `true` if at least one element in the collection satisfies the given predicate.

Question 5

What is a Sequence in Kotlin and how does it differ from a List?

Accepted Answer

Sequences are lazy; operations are applied one element at a time instead of creating intermediate lists

Answer

Kotlin `Sequence` is a lazy collection that processes elements one by one through a chain of operations, avoiding intermediate collection allocations.

Kotlin Practice Test

Kotlin Practice Test

Kotlin Kotlin Collections 2