Illustration of event loop in runBlocking

Example.kt

import kotlinx.coroutines.*

fun printCurrentThread(prefix: Int) {
    println("[$prefix] I'm in: " + Thread.currentThread().name)
}

fun main() {
    printCurrentThread(1)
    runBlocking {
        printCurrentThread(2)
        
        launch {
            printCurrentThread(3)
        }
        
        printCurrentThread(4)
        
        delay(100) // Just to suspend

        printCurrentThread(5)
    }
}

/*
Output:
[1] I'm in: main
[2] I'm in: main @coroutine#1
[4] I'm in: main @coroutine#1
[3] I'm in: main @coroutine#2
[5] I'm in: main @coroutine#1
*/