future to deferred.kt

fun <T : Any> Future<T>.toDeferred(
    scope: CoroutineScope = GlobalScope,
    waitTime: Long = 100
): Deferred<T> {
    val future = this
    val deferred = CompletableDeferred<T>()
    var isDone = false

    scope.launch {
        while (isActive && !isDone) {
            if (future.isDone) {
                try {
                    isDone = true
                    deferred.complete(future.get())
                } catch (e: Exception) {
                    isDone = true
                    deferred.completeExceptionally(e)
                }
            } else if (future.isCancelled) {
                isDone = true
                deferred.cancel()
            } else {
                delay(waitTime)
            }
        }
    }

    return deferred
}

suspend fun main(args: Array<String>) {
    val f: Future<String> = CompletableFuture.supplyAsync {
        Thread.sleep(2000)
        "Hello!"
    }

    val f1: Future<String> = CompletableFuture.supplyAsync {
        throw RuntimeException("Boom!")
    }

    listOf(f, f1).map { it.toDeferred() }.awaitAll().forEach { println(it) }
}