Most developers have written or used concurrent code during their careers. Those who use Java are probably familiar with the traditional unit of concurrency: the Thread. Kotlin brought first-class support to a different concurrency paradigm, called coroutines. These were developed in the sixties… Why are they relevant again, 50 years later? Let’s find out! This session intends to demonstrate the differences between concurrency models based on threads and concurrency models based on coroutines. We will discuss what coroutines are and what they are not, and answer questions such as: - How different are coroutines and Threads? - Are there any new pitfalls that developers should be aware of? - Do the traditional synchronization methods available in the JRE still apply? During the session, we’ll present several hands-on exercises that allow participants to see with their own eyes the way how coroutines work and experience the differences and similarities between Kotlin and Java concurrency models. We’ll discuss the performance, memory usage, and complexity of both models.

9. 1 thread Producer
2 while queue is not full
3 add new item to queue
1 thread Consumer
2 while queue is not empty
3 remove item from queue

10. 1 coroutine Producer
2 while queue is not full
3 add new item to queue
4 yield to Consumer
1 coroutine Consumer
2 while queue is not empty
3 remove item from queue
4 yield to Producer

11. 1 subroutine Producer
2 while queue is not full
3 add new item to queue
4 call Consumer
1 subroutine Consumer
2 while queue is not empty
3 remove item from queue
4 call Producer

14. runBlocking

17. yield()
delay()

18. 10
10

19. launch Job
cancel() -
join() -
yield()
isActive

20. .
. Did

21. withTimeout() -
withTimeoutOrNull() -

22. val one = async { doSomethingUsefulOne() }
Deferred Job
Deferred is
await() - awaits for completion without blocking and resumes when the result is available.

24. coroutineScope

29. kotlinx.coroutines.channels.Channel<E>

30. Have two coroutines communicating
through a channel.
Let’s try the experimental produce()
function.

32. fun foo(): Flow<Int> = flow { // flow builder
for (i in 1..3) {
emit(i) // emit next value
}
}
foo().collect { value -> println(value) }