Preconditions (require, check, error) in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check that the age is positive using require.

Kotlin

fun setAge(age: Int) {
    [1](age > 0) { "Age must be positive" }
    println("Age set to $age")
}

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

Aassert

Bcheck

Cerror

Drequire

Attempts:

3 left

💡 Hint

Common Mistakes

Using check instead of require, which is meant for state checks.

Using error which always throws an exception without condition.

The require function is used to check preconditions on function arguments. Here, it ensures age is positive.

2fill in blank

medium

Complete the code to verify that the user is logged in using check.

Kotlin

fun accessDashboard(loggedIn: Boolean) {
    [1](loggedIn) { "User must be logged in" }
    println("Access granted")
}

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

Arequire

Bcheck

Cerror

Dassert

Attempts:

3 left

💡 Hint

Common Mistakes

Using require which is for argument checks, not state.

Using error which throws unconditionally.

The check function is used to verify the state of the program. Here, it ensures the user is logged in before accessing the dashboard.

3fill in blank

hard

Fix the error in the code to throw an exception with a message if the list is empty.

Kotlin

fun processList(items: List<String>) {
    if (items.isEmpty()) [1]("List cannot be empty")
    println("Processing list")
}

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

Arequire

Bcheck

Cerror

Dassert

Attempts:

3 left

💡 Hint

Common Mistakes

Using require or check without a condition.

Not throwing any exception when the list is empty.

The error function throws an IllegalStateException with the given message unconditionally. It is used here to stop processing if the list is empty.

4fill in blank

hard

Fill both blanks to create a map of word lengths for words longer than 3 characters.

Kotlin

val words = listOf("apple", "bat", "carrot", "dog")
val lengths = words.associateWith { it.[1] }
    .filter { it.key.length [2] 3 }
println(lengths)

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Alength

B>

C<

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using count instead of length for string length.

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

The length property gives the length of the string. The filter keeps words with length greater than 3.

5fill in blank

hard

Fill all three blanks to create a map of uppercase words to their lengths for words longer than 3 characters.

Kotlin

val words = listOf("apple", "bat", "carrot", "dog")
val result = words.filter { it.length [1] 3 }
    .associateBy({ it.[2]() }, { it.[3] })
println(result)

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

A>

Buppercase

Clength

DtoUpperCase

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'uppercase' property which does not exist in Kotlin.

Using 'uppercase()' instead of 'toUpperCase()' in older Kotlin versions.

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

The filter keeps words longer than 3 characters using '>'. The toUpperCase() function converts words to uppercase keys. The length property gives the value.