Some beautiful examples of Kotlin

 1. UI Callbacks

var uirefreshListener: (()->Unit)? = null

this.uirefreshListener={
    showPostLoginUI()
}
@JvmStatic
fun addCustomerPremiumInfo(context: Context, customer_id: Int, callbackUI: (() -> Unit)?) {
}

2. Static fields and methods
companion object {
    @JvmStatic
    fun syncCustomerData(context: Context, name: String, email: String) {
}

3. Async and runonMainUI and co-routines

GlobalScope.async {
    val ackPurchaseResult = withContext(Dispatchers.IO) {
        billingClient.acknowledgePurchase(acknowledgePurchaseParams.build(),acknowledgePurchaseResponseListener)
    }
}