Why expressions over statements matters in Kotlin - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign the maximum of two numbers to max using an expression.

Kotlin

val max = if (a > b) [1] else b

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

Aa

B0

Ca + b

Db

Attempts:

3 left

💡 Hint

Common Mistakes

Using if as a statement without returning a value.

Assigning a fixed value like 0 instead of a.

The if expression returns a if a is greater than b, otherwise b. This assigns the maximum value to max.

2fill in blank

medium

Complete the code to assign the result of the expression that returns the length of the string or 0 if the string is null.

Kotlin

val length = str?.length ?: [1]

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

Anull

Bstr.length

C-1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using null as default which causes type mismatch.

Using str.length which can cause a null pointer exception.

The Elvis operator ?: returns 0 if str?.length is null, ensuring length is always an integer.

3fill in blank

hard

Fix the error in the expression that tries to assign the result of a when expression to a variable.

Kotlin

val result = when (x) {
    1 -> "One"
    2 -> "Two"
    else -> [1]
}

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Anull

B"Other"

Cprint("Other")

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using print("Other") which returns Unit, not String.

Returning null which may cause type mismatch.

The when expression must return a value for all cases. Using "Other" returns a string, matching the other branches.

4fill in blank

hard

Fill both blanks to create a map of words to their lengths, including only words longer than 3 characters.

Kotlin

val lengths = words.filter { word -> word.length > 3 }.map { word -> [1] to [2] }.toMap()

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Aword

Bword.length

Cword.uppercase()

Dword.count()

Attempts:

3 left

💡 Hint

Common Mistakes

Using word.uppercase() as key which changes the word.

Using word.count() which is not a Kotlin String method.

The map keys are the words themselves (word) and the values are their lengths (word.length), filtered by length > 3.

5fill in blank

hard

Fill all three blanks to create a map of uppercase words to their lengths, including only words longer than 4 characters.

Kotlin

val result = words.filter { word -> word.length [3] 4 }.map { word -> [1] to [2] }.toMap()

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

Aword.uppercase()

Bword.length

C>

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using word instead of uppercase for keys.

Using < instead of > for filtering.

The map keys are uppercase words (word.uppercase()), values are their lengths (word.length), filtered by words longer than 4 characters (> 4).