mayojava

fun showUserOrders(username: String, password: String) {
    val user = login(username, password)
    val orders = fetchUserOrders(user.userId)
    showUserOrders(orders)
}

fun login(username: String, password: String) { }

fun fetchUserOrders(userId: Long) { }

mayojava

fun showUserOrders(username: String, password: String) {
    login(username, password) {
        user -> fetchUserOrders(user.userId) {
            orders -> showUserOrders(orders)
        }
    }
}

fun login(username: String, password: String, callback: (User) -> Unit)

mayojava

fun showUserOrders(username: String, password: String) {
    login(username, password)
        .flatMap { user -> fetchUserOrders(user.userId) }
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe { showOrders(it) }
}

fun login(username: String, password: String): Single<User>

mayojava

fun showUserOrders(username: String, password: String) = GlobalScope.launch(Dispatchers.Main) {
    val user = withContext(Dispatchers.Default) { login(username, password) }
    val orders = withContext(Dispatchers.Default) { fetchUserOrders(user.userId) }
    showUserOrders(orders)
}

suspend fun login(username: String, password: String) { }

suspend fun fetchUserOrders(userId: Long) { }

mayojava

fun main(args: Array<String>) = runBlocking {
    repeat(100000) {
        launch {
            delay(100)
            println("coroutine $it")
        }
    }
}

mayojava

public fun withContext(
   context: CoroutineContext,
   block: suspend CorotuineScope.() -> T
): T

mayojava

fun main (args: Array<String>) = runBlocking {
    println("current thread: ${Thread.currentThread().name}")

    //switch to default Dispatcher
    val result = withContext(Dispatchers.Default) {
        delay(500)
        println("Thread: ${Thread.currentThread().name}")
        100
    }

mayojava

fun CoroutineScope.async(
   context: CoroutineContext = EmptyCorotuineContext,
   start: CoroutineStart = CoroutineStart.DEFAULT,
   block: suspend CoroutineScope.() -> Unit
): Deferred<T>

mayojava

fun main(args: Array<String>) = runBlocking {
   launch {
      delay(1_000)
      println("from launch coroutine body")
   }
   println("from runblocking")
}
//print
from runblocking
from launch coroutine body

mayojava

fun main(args: Array<String>) = runBlocking {
    val time = measureTimeMillis {
        val first = async { firstNumber() }
        val second = async { secondNumber() }
        val third = async { thirdNumber() }

        val result = first.await() + second.await() + third.await()
    }

    println(time) //prints 7 seconds