Set creation (setOf, mutableSetOf) in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kotlin code using setOf?

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

Kotlin

val fruits = setOf("apple", "banana", "apple", "orange")
println(fruits.size)

A 3

B 4

C 2

D Compilation error

💡 Hint

Remember that sets do not allow duplicate elements.

The setOf function creates an immutable set that automatically removes duplicates. Since "apple" appears twice, the set size is 3.

❓ Predict Output

intermediate

What happens when you add an element to a setOf collection?

Look at this Kotlin code. What will happen when it runs?

Kotlin

val numbers = setOf(1, 2, 3)
numbers.add(4)

A Compilation error: add() is not available

B 4 is added to the set

C Runtime exception: UnsupportedOperationException

D The set remains unchanged silently

💡 Hint

setOf creates an immutable set.

The set created by setOf is immutable. Calling add() causes a runtime UnsupportedOperationException.

❓ Predict Output

advanced

What is the output of this Kotlin code using mutableSetOf?

Analyze this Kotlin code and determine what it prints.

Kotlin

val mutableSet = mutableSetOf("cat", "dog")
mutableSet.add("bird")
mutableSet.remove("dog")
println(mutableSet.size)

A 3

B 1

C Compilation error

D 2

💡 Hint

mutableSetOf creates a set you can change.

Initially, the set has 2 elements. Adding "bird" makes 3, then removing "dog" leaves 2 elements.

🧠 Conceptual

advanced

Which statement about setOf and mutableSetOf is true?

Choose the correct statement about Kotlin's setOf and mutableSetOf functions.

A setOf creates an immutable set, mutableSetOf creates a mutable set

B Both setOf and mutableSetOf create mutable sets

C Both setOf and mutableSetOf create immutable sets

D setOf creates a mutable set, mutableSetOf creates an immutable set

💡 Hint

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

setOf creates an immutable set that cannot be changed after creation. mutableSetOf creates a mutable set that can be changed.

🔧 Debug

expert

Why does this Kotlin code throw an exception?

This Kotlin code throws an exception at runtime. What is the cause?

Kotlin

val mySet = setOf("a", "b", "c")
mySet.remove("b")

A remove() requires a mutable list, not a set

B remove() is not supported on immutable sets created by setOf

C The element "b" does not exist in the set

D The code has a syntax error

💡 Hint

Check if the set is mutable or immutable.

setOf creates an immutable set. Calling remove() on it causes UnsupportedOperationException at runtime.