Mutable vs immutable interfaces in Kotlin - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an immutable list in Kotlin.

Kotlin

val numbers: List<Int> = [1](1, 2, 3)

Drag options to blanks, or click blank then click option'

AlistOf

BmutableListOf

CarrayListOf

DsetOf

Attempts:

3 left

💡 Hint

Common Mistakes

Using mutableListOf instead of listOf, which creates a mutable list.

In Kotlin, listOf creates an immutable list, which means you cannot change its elements after creation.

2fill in blank

medium

Complete the code to add an element to a mutable list in Kotlin.

Kotlin

val numbers = mutableListOf(1, 2, 3)
numbers.[1](4)

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Aset

Bremove

Cclear

Dadd

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'set' which replaces an element instead of adding.

Using 'remove' which deletes an element.

The add function adds an element to a mutable list in Kotlin.

3fill in blank

hard

Fix the error in the code by choosing the correct interface to declare a mutable list.

Kotlin

val numbers: [1]<Int> = mutableListOf(1, 2, 3)

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AMutableList

BSet

CList

DCollection

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'List' which is immutable and causes errors when modifying.

To declare a mutable list interface in Kotlin, use MutableList. The List interface is read-only.

4fill in blank

hard

Fill both blanks to create an immutable map from a mutable map in Kotlin.

Kotlin

val mutableMap = mutableMapOf("a" to 1, "b" to 2)
val immutableMap: [1]<String, Int> = mutableMap
val readOnlyMap: [2]<String, Int> = immutableMap

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AMap

BMutableMap

CHashMap

DLinkedHashMap

Attempts:

3 left

💡 Hint

Common Mistakes

Using MutableMap for immutableMap causes mutability.

Both immutableMap and readOnlyMap use the Map interface, which is read-only in Kotlin.

5fill in blank

hard

Fill all three blanks to filter a mutable list and create an immutable list in Kotlin.

Kotlin

val mutableList = mutableListOf(1, 2, 3, 4, 5)
val filteredList: [1]<Int> = mutableList.[2] { it [3] 3 }

Drag options to blanks, or click blank then click option'

AList

Bfilter

C>

DMutableList

Attempts:

3 left

💡 Hint

Common Mistakes

Using MutableList as the type causes confusion about mutability.

Using '<' instead of '>' changes the filter condition.

The filter function returns a new List (immutable) containing elements greater than 3.