Let function behavior and use cases in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use the let function to print the length of the string.

Kotlin

val name: String? = "Kotlin"
name?.[1] {
    println("Length: ${it.length}")
}

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

Alet

Brun

Capply

Dalso

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'run' instead of 'let' which doesn't pass the object as 'it' in this context.

Using 'apply' which uses 'this' instead of 'it'.

Using 'also' which returns the original object but is less common for this use case.

The let function is used here to execute the block only if name is not null, and it refers to the non-null value.

2fill in blank

medium

Complete the code to safely convert a nullable string to uppercase using let.

Kotlin

val input: String? = "hello"
val result = input?.[1] {
    it.uppercase()
} ?: "DEFAULT"

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Aalso

Blet

Cwith

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'also' which returns the original object, not the block result.

Using 'run' without safe call operator, which can cause null pointer exceptions.

Using 'with' which is not an extension function and requires the object as argument.

let is used to safely call uppercase() on the non-null input. If input is null, it returns "DEFAULT".

3fill in blank

hard

Fix the error in the code by choosing the correct function to chain calls and return the last expression.

Kotlin

val number = 5
val result = number.[1] {
    println("Number is $it")
    it * 2
}
println(result)

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Aapply

Brun

Calso

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'also' which returns the original object, so result would be 5, not 10.

Using 'apply' which uses 'this' and returns the original object.

Using 'run' which uses 'this' and is not called as extension here.

let returns the result of the last expression in the block, so result will be 10. also returns the original object, not the block result.

4fill in blank

hard

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

Kotlin

val words = listOf("cat", "house", "dog", "elephant")
val lengths = words.associateWith { it.[1] }
    .filter { it.value [2] 3 }

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Alength

Bcount

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'count' instead of 'length'; 'count' requires a predicate and does not return total length.

Using '<' instead of '>' which would filter shorter words instead.

Using 'count' without parentheses which is a function.

length returns the length of the string. The filter keeps entries where the length is greater than 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 words = listOf("apple", "bat", "carrot", "dog")
val result = words.filter { it.length [1] 4 }
    .associateBy({ it.[2]() }, { it.[3] })

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

A>

Buppercase

Clength

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' in filter condition.

Using 'lowercase' instead of 'uppercase' for keys.

Using 'length' without parentheses if it was a function (it's a property).

The filter keeps words longer than 4 characters. associateBy creates a map with uppercase words as keys and their lengths as values.