List creation (listOf, mutableListOf) in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an immutable list of integers.

Kotlin

val numbers = [1](1, 2, 3, 4, 5)

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 creates a mutable list.

Using setOf creates a set, not a list.

The listOf function creates an immutable list in Kotlin.

2fill in blank

medium

Complete the code to create a mutable list of strings.

Kotlin

val fruits = [1]("apple", "banana", "cherry")

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

AlistOf

BsetOf

CmutableListOf

DarrayOf

Attempts:

3 left

💡 Hint

Common Mistakes

Using listOf creates an immutable list that cannot be changed.

Using arrayOf creates an array, not a list.

The mutableListOf function creates a mutable list that can be changed later.

3fill in blank

hard

Fix the error in the code to create a mutable list of doubles.

Kotlin

val prices = [1](10.5, 20.0, 30.75)

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

AsetOf

BarrayListOf

ClistOf

DmutableListOf

Attempts:

3 left

💡 Hint

Common Mistakes

Using listOf creates an immutable list that cannot be changed.

Using setOf creates a set, not a list.

To create a mutable list, use mutableListOf. listOf creates an immutable list.

4fill in blank

hard

Fill both blanks to create an immutable list and get its size.

Kotlin

val colors = [1]("red", "green", "blue")
val size = colors.[2]

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

AlistOf

BmutableListOf

Csize

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using mutableListOf instead of listOf for an immutable list.

Using count() instead of size property.

listOf creates an immutable list, and size gets the number of items in the list.

5fill in blank

hard

Fill all three blanks to create a mutable list, add an item, and get the last element.

Kotlin

val animals = [1]("cat", "dog")
animals.[2]("rabbit")
val last = animals.[3]()

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

AmutableListOf

Badd

Clast

DlistOf

Attempts:

3 left

💡 Hint

Common Mistakes

Using listOf instead of mutableListOf for a mutable list.

Using size instead of last() to get the last element.

mutableListOf creates a mutable list, add adds an item, and last() gets the last element.

Practice

1. Which Kotlin function creates a list that cannot be changed after it is created?

easy

A. listOf

B. mutableListOf

C. arrayListOf

D. setOf

Solution

1. Step 1: Understand listOf behavior

   listOf creates a fixed list that cannot be changed after creation.

2. Step 2: Compare with mutableListOf

   mutableListOf creates a list that can be changed (add/remove items).

3. Final Answer:

   listOf -> Option A

4. Quick Check:

   Fixed list = listOf [OK]

Hint: Use listOf for fixed lists, mutableListOf for changeable lists [OK]

Common Mistakes:

• Confusing mutableListOf as fixed list
• Thinking arrayListOf is immutable
• Using setOf which creates a set, not a list

2. Which of the following is the correct syntax to create a mutable list of integers with values 1, 2, and 3?

easy

A. val list = listOf(1, 2, 3)

B. val list = mutableListOf(1, 2, 3)

C. val list = mutableList(1, 2, 3)

D. val list = list(1, 2, 3)

Solution

1. Step 1: Identify correct function name

   The correct function to create a mutable list is mutableListOf.

2. Step 2: Check syntax correctness

   Options C and D use invalid function names. val list = listOf(1, 2, 3) creates an immutable list.

3. Final Answer:

   val list = mutableListOf(1, 2, 3) -> Option B

4. Quick Check:

   Mutable list syntax = mutableListOf(...) [OK]

Hint: Remember mutableListOf has 'Of' at the end [OK]

Common Mistakes:

• Using listOf instead of mutableListOf for mutable lists
• Misspelling mutableListOf as mutableList
• Using list() which does not exist

3. What will be the output of this Kotlin code?

val list = listOf("apple", "banana", "cherry")
println(list[1])

medium

A. banana

B. IndexOutOfBoundsException

C. cherry

D. apple

Solution

1. Step 1: Understand list indexing

   Kotlin lists use zero-based indexing, so index 1 refers to the second item.

2. Step 2: Identify the item at index 1

   The list is ["apple", "banana", "cherry"], so index 1 is "banana".

3. Final Answer:

   banana -> Option A

4. Quick Check:

   Index 1 = second item = banana [OK]

Hint: Remember list indexes start at 0 in Kotlin [OK]

Common Mistakes:

• Thinking index 1 is the first item
• Expecting an error for valid index
• Confusing listOf with mutableListOf output

4. What is wrong with this Kotlin code?

val list = listOf(1, 2, 3)
list.add(4)

medium

A. add() method requires a mutableListOf list

B. Syntax error in listOf declaration

C. listOf creates an immutable list; add() is not allowed

D. No error; code runs fine

Solution

1. Step 1: Check list type

   listOf creates an immutable (read-only) list.

2. Step 2: Understand add() method

   The add() method is only available on mutable lists, not on immutable lists.

3. Final Answer:

   listOf creates an immutable list; add() is not allowed -> Option C

4. Quick Check:

   Immutable list cannot add items [OK]

Hint: Use mutableListOf to add or remove items [OK]

Common Mistakes:

• Trying to add to listOf list
• Ignoring immutability of listOf
• Assuming add() works on all lists

5. You want to create a list of strings that you can add items to later. Which Kotlin code correctly creates this list and adds "orange" to it?

hard

A. val fruits = mutableListOf("apple", "banana")
fruits = fruits + "orange"

B. val fruits = listOf("apple", "banana")
fruits.add("orange")

C. val fruits = listOf("apple", "banana")
fruits += "orange"

D. val fruits = mutableListOf("apple", "banana")
fruits.add("orange")

Solution

1. Step 1: Choose a mutable list

   To add items later, the list must be mutable, so use mutableListOf.

2. Step 2: Use add() method correctly

   Calling add("orange") on a mutable list adds the item successfully.

3. Step 3: Check other options

   val fruits = listOf("apple", "banana") fruits.add("orange") tries to add to immutable list (error). val fruits = listOf("apple", "banana") fruits += "orange" uses += on immutable list (creates new list but does not modify original). val fruits = mutableListOf("apple", "banana") fruits = fruits + "orange" tries to reassign val which is not allowed.

4. Final Answer:

   val fruits = mutableListOf("apple", "banana") fruits.add("orange") -> Option D

5. Quick Check:

   Mutable list + add() = correct way [OK]

Hint: Use mutableListOf and add() to change list after creation [OK]

Common Mistakes:

• Adding to immutable list
• Trying to reassign val variable
• Using += on immutable list expecting mutation