Why coroutines matter for async programming in Kotlin - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to launch a coroutine that prints "Hello".

Kotlin

import kotlinx.coroutines.*

fun main() = runBlocking {
    launch [1] {
        println("Hello")
    }
}

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

A()

B() -> Unit

C{}

DUnit

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses () instead of curly braces {} for the coroutine block.

Passing a function type instead of a lambda block.

The launch function takes a lambda block denoted by curly braces {} to define the coroutine's code.

2fill in blank

medium

Complete the code to suspend the coroutine for 1000 milliseconds.

Kotlin

import kotlinx.coroutines.*

suspend fun waitOneSecond() {
    [1](1000L)
}

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Adelay

Bsleep

Cpause

Dwait

Attempts:

3 left

💡 Hint

Common Mistakes

Using Thread.sleep which blocks the thread instead of suspending the coroutine.

Using wait or pause which are not coroutine functions.

The delay function suspends the coroutine without blocking the thread.

3fill in blank

hard

Fix the error in the coroutine builder to properly start a coroutine.

Kotlin

import kotlinx.coroutines.*

fun main() {
    GlobalScope.launch [1] {
        println("Running")
    }
    Thread.sleep(500L)
}

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

A{}

B() -> Unit

C()

DUnit

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses () instead of curly braces {} for the coroutine block.

Passing a function type instead of a lambda block.

launch requires a lambda block with curly braces {} to define the coroutine's code.

4fill in blank

hard

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

Kotlin

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

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Ait.length

B>

C<

Dit.size

Attempts:

3 left

💡 Hint

Common Mistakes

Using it.size which is not valid for String.

Using < instead of > for filtering longer words.

Use it.length to get word length and > 3 to filter longer words.

5fill in blank

hard

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

Kotlin

val words = listOf("apple", "bat", "carrot", "dog")
val result = words.associateBy(
    keySelector = { [1] },
    valueTransform = { [2] }
).filter { it.value [3] 4 }

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Ait.uppercase()

Bit.length

C>

Dit.toUpperCase()

Attempts:

3 left

💡 Hint

Common Mistakes

Using deprecated it.toUpperCase() instead of it.uppercase().

Using < instead of > for filtering.

Mixing keySelector and valueTransform parameters.

Use it.uppercase() for uppercase keys, it.length for values, and > 4 to filter.