Kotlin 2 cheatsheet

Kotlin 2: Coroutines

6 common Kotlin 2 tasks.

Add coroutines

Coroutine support is a separate library. Add it to your Gradle dependencies.

implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.10.2")

runBlocking bridges regular code to coroutines. launch starts concurrent work and returns a Job.

import kotlinx.coroutines.*

fun main() = runBlocking {
    launch {
        delay(100)
        println("world")
    }
    println("hello")
}

async starts work that returns a value, and await gets it. Both calls below run at the same time.

suspend fun total(): Int = coroutineScope {
    val a = async { fetchA() }
    val b = async { fetchB() }
    a.await() + b.await()
}

Run blocking or CPU-heavy work on a suitable dispatcher without blocking the caller.

val text = withContext(Dispatchers.IO) { File("data.txt").readText() }

A flow emits values over time and is collected from a coroutine.

fun ticks(): Flow<Int> = flow {
    for (i in 1..3) {
        delay(100)
        emit(i)
    }
}

ticks().collect { println(it) }

Cancel a block that takes too long.

val result = withTimeoutOrNull(1_000) { slowCall() }