happy-bracket

class SetBackedMap<K, V>(private val set: Set<Map.Entry<K, V>>) : Map<K, V> {

    override val entries: Set<Map.Entry<K, V>> = set
    override val keys: Set<K> = set.map { (key, _) -> key }.toSet()
    override val size: Int = set.size
    override val values: Collection<V> = set.map { (_, value) -> value }

    override fun containsKey(key: K): Boolean {
        return set.any { (possibleKey, _) -> possibleKey == key }
    }

happy-bracket

Single.just(3).map { x -> x.toString() }

happy-bracket

object Sentries {

    private val callbacks = ConcurrentHashMap<Reference<*>, () -> Unit>()
    private val refs = HashSet<WeakReference<*>>()
    private val refQueue = ReferenceQueue<Sentry<*>>()
    private val poller =
        Observable.interval(10000, TimeUnit.MILLISECONDS)
            .subscribe {
                refQueue.poll()?.let { ref ->
                    callbacks.remove(ref)?.invoke()