List creation (listOf, mutableListOf) in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kotlin code?

Consider the following Kotlin code snippet. What will be printed?

Kotlin

val list = listOf(1, 2, 3)
println(list.size)
println(list[1])

A 3\n2

B 2\n1

C 3\n1

D 2\n3

💡 Hint

Remember that listOf creates an immutable list and indexing starts at 0.

The list has 3 elements: 1, 2, and 3. The size is 3. The element at index 1 is the second element, which is 2.

❓ Predict Output

intermediate

What happens when you try to add an element to a listOf list?

What will happen when running this Kotlin code?

Kotlin

val list = listOf(10, 20, 30)
list.add(40)

A Runtime exception: UnsupportedOperationException

B Compilation error: val cannot be reassigned

C The element 40 is added successfully

D Compilation error: Unresolved reference 'add'

💡 Hint

listOf creates an immutable list without add method.

listOf returns an immutable list which does not have an add method. Trying to call add causes a compilation error because the method does not exist.

❓ Predict Output

advanced

What is the output of this Kotlin code using mutableListOf?

Analyze the following Kotlin code and select the output:

Kotlin

val mutableList = mutableListOf("a", "b")
mutableList.add("c")
println(mutableList.size)
println(mutableList[2])

A 3\nb

B 2\nc

C 3\nc

D RuntimeException: IndexOutOfBoundsException

💡 Hint

mutableListOf creates a list you can change by adding elements.

The mutable list starts with 2 elements. After adding "c", size becomes 3. The element at index 2 is "c".

🧠 Conceptual

advanced

Which statement about listOf and mutableListOf is true?

Choose the correct statement about Kotlin's listOf and mutableListOf functions.

A listOf creates a mutable list; mutableListOf creates an immutable list

B listOf creates an immutable list; mutableListOf creates a mutable list

C Both listOf and mutableListOf create immutable lists

D Both listOf and mutableListOf create mutable lists

💡 Hint

Think about whether you can add or remove elements after creation.

listOf creates a list that cannot be changed after creation (immutable). mutableListOf creates a list that can be changed (mutable).

❓ Predict Output

expert

What is the output of this Kotlin code involving list creation and modification?

Examine this Kotlin code and select the output:

Kotlin

val list1 = listOf(1, 2, 3)
val list2 = list1.toMutableList()
list2.add(4)
println(list1.size)
println(list2.size)

A 3\n4

B 4\n4

C 3\n3

D RuntimeException: UnsupportedOperationException

💡 Hint

toMutableList creates a new mutable copy of the original list.

list1 is immutable with size 3. list2 is a mutable copy, so after adding 4, its size is 4. list1 remains size 3.