fun main(args: Array<String>) {

    assert(Prefs.lastLogin == "")
    assert(Prefs.updateDate == 0L)

    Prefs.lastLogin = "some login"
    Prefs.updateDate = 12345L

    assert(Prefs.lastLogin == "some login")
    assert(Prefs.updateDate == 12345L)
}

val preferenceImitator = mutableMapOf<String, Any>()

class Prefs {
    private class PrefSaver<T>(var key: String, var defValue: T) {

        @Suppress("UNCHECKED_CAST")
        var value: T
            get() {
                val temp =  when (defValue) {
                    is Boolean -> preferenceImitator[key] as? T ?: defValue
                    is Long -> preferenceImitator[key] as T ?: defValue
                    is String -> preferenceImitator[key] as T ?: defValue
                    is Int -> preferenceImitator[key] as T ?: defValue
                    is Float -> preferenceImitator[key] as T ?: defValue
                    is MutableSet<*> -> preferenceImitator[key] as T ?: defValue
                    else -> throw ClassNotFoundException()
                }
                println("Get value '$temp' with key '$key'")
                return temp
            }
            set(value) {
                println("Set value '$value' with key '$key'")
                preferenceImitator[key] = when (defValue) {
                    is Boolean -> value
                    is Long -> value
                    is String -> value
                    is Int -> value
                    is Float -> value
                    is MutableSet<*> -> value
                    else -> throw ClassNotFoundException()
                } as Any
            }
    }

    companion object {
        var updateDate = PrefSaver("update_date", 0L).value
        var lastLogin = PrefSaver("login", "").value
    }
}