Why immutability by default matters in Kotlin - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an immutable variable in Kotlin.

Kotlin

val number = [1]

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

Avar

B10

Cmutable

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'var' instead of a value for assignment.

Trying to assign 'val' as a value.

In Kotlin, val declares an immutable variable, and number is assigned the value 10.

2fill in blank

medium

Complete the code to declare a mutable variable in Kotlin.

Kotlin

var count = [1]

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

A5

Bval

Cvar

Dimmutable

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'var' as the value instead of a number.

Using 'val' as the value.

The variable count is mutable and initialized with the value 5.

3fill in blank

hard

Fix the error in the code by choosing the correct keyword for immutability.

Kotlin

[1] message = "Hello"

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

Avar

Bmutable

Cconst

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'var' which allows the variable to be changed.

Using 'const' which is not valid here.

val declares an immutable variable, which is the correct keyword here.

4fill in blank

hard

Fill both blanks to create a list that cannot be changed and a list that can be changed.

Kotlin

val immutableList = listOf(1, 2, 3)
[2] mutableList = [1](1, 2, 3)

mutableList = listOf(4, 5, 6)

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AmutableListOf

Bval

Cvar

DlistOf

Attempts:

3 left

💡 Hint

Common Mistakes

Using listOf for mutable list.

Using val for mutable list variable.

mutableListOf creates a mutable list, and var allows reassignment of mutableList.

5fill in blank

hard

Fill all three blanks to create a map with immutable keys and values, filtering only entries with values greater than 10.

Kotlin

val data = mapOf("a" to 5, "b" to 15, "c" to 20)
val filtered = data.filter { ([1], [2]) -> [3] > 10 }

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

Akey

Bvalue

Dk

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same name for key and value.

Using incorrect variable names that don't match the lambda destructuring.

The lambda destructures the map entry into k and value, then filters entries where value is greater than 10.