Correctly implementing wait and notify in Kotlin

Question

According to this document, using wait and notify is discouraged in Kotlin: https://kotlinlang.org/docs/reference/java-interop.html

Answer 1

You could use the kotlin Semaphore to suspend the coroutine instead of blocking a thread:

val semaphore = Semaphore(1, 0)

suspend fun runFetchLoop() = withContext(Dispatchers.Default){
    while (isActive) {
        val data = fetchData()
        processData(data)
        semaphore.acquire()
        if (data.isEmpty()) {
            semaphore.acquire()
        }
        semaphore.release()
    }
}

fun notifyDataAvailable() = semaphore.release()

Here is a running example: https://pl.kotl.in/bnKeOspfs .

However I would prefer a cold Flow or a hot Channel to solve this problem. Here is a good article about cold flows and hot channels of the great Roman Elizarov