Async and await for concurrent results in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does async do in Kotlin coroutines?

async starts a coroutine that runs concurrently and returns a Deferred object, which represents a future result.

beginner

What is the purpose of await() in Kotlin coroutines?

await() is called on a Deferred to suspend the coroutine until the result is ready, then returns the result.

intermediate

How does using async and await help with concurrency?

They allow multiple tasks to run at the same time without blocking, improving efficiency by waiting only when results are needed.

beginner

What type does async return in Kotlin coroutines?

async returns a Deferred<T>, where T is the type of the result.

beginner

Can you use await() outside of a coroutine?

No, await() must be called inside a coroutine or suspend function because it suspends execution.

What does async return in Kotlin coroutines?

A Deferred<T>

B Job

C Unit

D List<T>

async returns a Deferred<T>, which represents a future result.

What happens when you call await() on a Deferred?

A It immediately returns null

B It suspends until the result is ready and returns it

C It cancels the coroutine

D It starts a new coroutine

await() suspends the coroutine until the result is ready, then returns the result.

Why use async and await together?

A To create infinite loops

B To block the main thread

C To run tasks concurrently and get results later

D To handle exceptions only

They let you run tasks at the same time and wait for their results when needed.

Can await() be called outside a coroutine?

A No, it must be inside a coroutine or suspend function

B Yes, anytime

C Only in main function

D Only in Java code

await() suspends execution, so it must be called inside a coroutine or suspend function.

What is the main benefit of using async in Kotlin?

A Avoiding coroutines

B Making code slower

C Blocking the UI thread

D Running multiple tasks concurrently

async helps run tasks at the same time, improving performance.

Explain how async and await work together to run tasks concurrently in Kotlin.

Think about starting a task and waiting for its answer later.

Describe why you cannot call await() outside a coroutine or suspend function.

Consider what happens when you wait for a result in Kotlin coroutines.