Async coroutine builder in Kotlin - Mini Project: Build & Apply

Async coroutine builder

📖 Scenario: You are building a simple Kotlin program that uses asynchronous coroutines to fetch data without blocking the main thread. This is like ordering food at a restaurant and waiting for it to be prepared while you relax, instead of standing at the counter waiting.

🎯 Goal: Create a Kotlin program that uses the async coroutine builder to start a background task that returns a result, then waits for the result and prints it.

📋 What You'll Learn

Create a coroutine scope using runBlocking

Use the async builder to start a coroutine that returns a string

Use await() to get the result from the async coroutine

Print the result to the console

💡 Why This Matters

🌍 Real World

Async coroutines let programs do work in the background without freezing the app, like loading images or fetching data while you keep using the app.

💼 Career

Understanding async coroutines is important for Kotlin developers working on Android apps or backend services to write efficient, responsive code.

1

Setup coroutine scope

Write a Kotlin program that starts with fun main() and inside it, create a coroutine scope using runBlocking.

Kotlin

fun main() {
    // Create a coroutine scope using runBlocking
    // Your code here
}

Need a hint?

Use runBlocking { } inside main to create a coroutine scope.

2

Start async coroutine

Inside the runBlocking block, create a variable called deferred and assign it to an async coroutine that returns the string "Hello from async".

Kotlin

import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.async

fun main() {
    runBlocking {
        // Create async coroutine that returns "Hello from async"
        // Your code here
    }
}

Need a hint?

Use val deferred = async { "Hello from async" } inside runBlocking.

3

Await async result

Use await() on the deferred variable to get the result and store it in a variable called result.

Kotlin

import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.async

fun main() {
    runBlocking {
        val deferred = async {
            "Hello from async"
        }
        // Await the result from deferred
        // Your code here
    }
}

Need a hint?

Use val result = deferred.await() to get the async result.

4

Print the result

Print the result variable using println inside the runBlocking block.

Kotlin

import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.async

fun main() {
    runBlocking {
        val deferred = async {
            "Hello from async"
        }
        val result = deferred.await()
        // Print the result
        // Your code here
    }
}

Need a hint?

Use println(result) to display the message.