Functional Kotlin

Java Futures

As callback style tends to be hard to maintain, other styles have emerged in recent years. One of these styles is futures. A future is a computation that may complete in the future. When we invoke the Future.get method, it will obtain its result, but we also block the thread:

import java.util.concurrent.ExecutorServiceimport java.util.concurrent.Executorsclass FutureUserService(private val userClient: UserClient,                  private val factClient: FactClient,                  private val userRepository: UserRepository,                  private val factRepository: FactRepository) : UserService {   override fun getFact(id: UserId): Fact {      val executor = Executors.newFixedThreadPool(2)      val user = executor.submit<User?> { userRepository.getUserById(id) }.get()      return if (user ...