adam-arold

val reference = KotlinFilterOperation()::filterBy

adam-arold

public class JavaUser {
 
    // ...
    
    public static Set<String> fetchCitiesOfUsers(
                                  List<JavaUser> users) {
        return users.stream()
                .flatMap(user -> user.addresses.stream())
                .map(JavaUser.Address::getCity)
                .collect(Collectors.toSet());

adam-arold

fun fetchCitiesOfUsers(users: List<KotlinUser>) = users
            .flatMap(KotlinUser::addresses)
            .map(Address::city)
            .toSet()

adam-arold

public class KotlinInterop {

    public void helloJava() {
        System.out.println("Hello from Java!");
    }

    public void helloKotlin() {
        JavaInterop.createInstance().helloKotlin();
    }
}

adam-arold

class JavaInterop {

    fun helloJava() {
        KotlinInterop().helloJava()
    }

    fun helloKotlin() {
        println("Hello from Kotlin!")
    }

adam-arold

class Foo {
    private val c: String
    init {
        bar()
        c = ""
    }
    private fun bar() {
        println(c.length)
    }
}

adam-arold

val map = ConcurrentHashMap<String, String>()
map["foo"] = "bar"
val bar: String = map["foo"]!!

adam-arold

val queue: Queue<String> = LinkedList()
queue.peek().toInt()

adam-arold

/**
  * Retrieves, but does not remove, the head of this queue,
  * or returns {@code null} if this queue is empty.
  *
  * @return the head of this queue, or {@code null} if this queue is empty
  */
  E peek();

adam-arold

val queue: Queue<String?> = LinkedList()
queue.peek()?.toInt()