Coroutine Coding Quiz

Test your Kotlin coroutine knowledge with this quiz! I’m planning to create multiple coroutine quizzes ranging from beginner to advanced levels. Each question has three choices in expandable sections, and you’ll need to click to reveal the answer and explanation.

Q1

What will be the output of this code?

fun main(args: Array<String>) {
    runBlocking {
        println("result is ${myFun()}")
    }
}

suspend fun myFun(): Int {
    return coroutineScope {
        var x = 0
        launch {
            delay(1000)
            x += 100
        }

        launch {
            delay(3000)
            x += 200
        }
        return@coroutineScope x
    }
}

Choices

• result is 0
• result is 300
• doesn’t compile

Answer

Q2

What will be the output of this code

fun main(args: Array<String>) {
    runBlocking {
        repeat(4) { x ->
            println("${myFun(x)}")
        }
        println("done")
    }
}

suspend fun myFun(x: Int): Int = coroutineScope {
    val handler = CoroutineExceptionHandler { context, throwable ->
        println("caught")
    }
    return@coroutineScope async(handler + SupervisorJob()) {
        if (x == 2) {
            throw IOException("bhoom!")
        }
        x
    }.await()
}

Choices

• 0, 1, caught, 3, done
• 0, 1, process die with IOException
• 0, 1, caught, done

Answer