Hands-On Object-Oriented Programming with Kotlin

Non-cancelable block

The launch function returns an instance of the Job class, which means that a coroutine can be cancelled at any time. In this case, if we have a long-term operation in the finally block, JobCancellationException will be thrown.

The following example shows a case like this:

fun main(args: Array<String>) = runBlocking<Unit> {    val job = launch {        try {            delay(1000000)        } finally {            try {                println("start")                delay(1000)                println("end")            } catch (exception: Exception) {                exception.printStackTrace()            }        }    }    delay(500)    job.cancel()    job.join()}

The following is the output:

kotlinx.coroutines.experimental.JobCancellationException: Job was cancelled normally; job=StandaloneCoroutine{Cancelling}@7f77b211 start

As you can see, the finally block ...