await Result in Kotlin

Introduction

await Result is a fundamental concept every Kotlin developer should understand. async starts parallel work and await retrieves its result. Together they compose concurrent operations without manual thread management.

Await suspends until Deferred completes and returns value. In this tutorial you will learn the syntax, walk through a complete example program, study the sample output, and review best practices so you can apply the concept confidently in your own projects.

Definition

• await suspends until Deferred completes and returns value.
• If async block throws, exception is rethrown at await call.
• Combine multiple await calls for parallel tasks.

Syntax

deferred.await()

await Result in Kotlin Example Program in Kotlin

import kotlinx.coroutines.*

suspend fun load(id: Int): Int {
    delay(50)
    return id * 10
}

fun main(args: Array<String>) = runBlocking {
    val d1 = async { load(1) }
    val d2 = async { load(2) }
    println(d1.await() + d2.await())
}

Sample Output

30

When to use

Use async/await when you have independent tasks that can run in parallel and you need to combine their results.

How it works

1. The program starts with a main function — the entry point that runs when you execute the file.

2. suspend fun load(id: Int): Int { shows coroutine-based concurrency — work runs without blocking the calling thread.

3. val d1 = async { load(1) } assigns or updates a value used later in the program.

4. val d2 = async { load(2) } assigns or updates a value used later in the program.

5. The println(d1.await() + d2.await()) statement writes a line to the console — this produces part of the sample output below.

6. Await suspends until Deferred completes and returns value.

7. Run the program in IntelliJ IDEA, Android Studio, or with the Kotlin command-line compiler (kotlinc / kotlin). Compare your console output with the sample output shown below.

Best Practices

Common Mistakes

Key Points

• await suspends until Deferred completes and returns value.
• If async block throws, exception is rethrown at await call.
• Combine multiple await calls for parallel tasks.
• Test the example locally and verify the output matches the sample.
• Experiment by changing input values to see how behaviour changes.

Notes

• Add the kotlinx-coroutines-core dependency when running coroutine examples outside Android or IntelliJ.
• Semicolons at the end of statements are optional in Kotlin.