Kotlin or The Quest For Java.Next

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Kotlin or The Quest For Java.Next [email protected]

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Java.Next ? ? ?

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JRuby? Jython? Groovy?

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Clojure?

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Gosu? Fantom? Mirah?

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Scala?

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Ceylon?

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Xtend?

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Kotlin?

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Java 8?

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Java 8!

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However...

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I think that Kotlin is a pretty good one

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kotlin.jetbrains.org kotlin-demo.jetbrains.com

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Hello, world! package _01hello fun main(args: Array) { println("Hello, world!") }

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Classes package _02classes class Person1(name: String) { val name: String { this.name = name } }

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Classes package _02classes class Person2(name: String) { val name: String = name }

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Classes package _02classes class Person3(val name: String) fun main(args: Array) { val person = Person3("Ladislav Thon") println(person) }

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Classes package _02classes data class Person4(val name: String) fun main(args: Array) { val person = Person4("Ladislav Thon") println(person) }

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Traits package _03traits trait Foo { fun foo(): String } trait Bar { fun bar() = "bar" }

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Traits package _03traits class Fubar : Foo, Bar { override fun foo() = "foo" fun fubar() { println("${foo()}-${bar()}") } }

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Multiple Inheritance? ● single inheritance + interfaces ○ Java <= 7, C# ● stateless traits ○ Kotlin, Ceylon, Java 8 (kind of…) ● stateful traits ○ PHP >= 5.4 (I think…) ● mixins ○ Scala, Dart ● full multiple inheritance ○ C++

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Null Safety & Smart Casts package _04nullSafety fun main(args: Array) { val maybeAnswer: Int? = ... if (maybeAnswer != null) { val answer: Int = maybeAnswer } }

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Null Safety & Safe Navigation & Elvis package _04nullSafety fun main(args: Array) { val answer: Int? = … val doubleAnswer = answer?.let { it * 2 } answer?.times { println("Hi!") } val question = answer ?: 42 }

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Collections package _05collections fun print(nums: Collection) { println(nums) } fun add(nums: MutableCollection) { nums.add(4) }

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Generics package _06generics trait Producer { fun produce(): T } trait Consumer{ fun consume(t: T) }

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Generics package _06generics trait Holder { fun produce(): T fun consume(t: T) } fun use(h: Holder) { h.produce() }

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Extension Methods package _07extensions fun String.pirateStyle() = "Arrr! ${this.capitalize()}" fun main(args: Array) { println("hello, world".pirateStyle()) }

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Lambdas package _08lambdas fun main(args: Array) { val nums = arrayListOf(1, 2, 3, 4, 5, 6, 7) .filter { it % 2 == 0 } .flatMap { listOf(it, it * 2, it * 3) } .takeWhile { it < 10 } println(nums) }

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Lambdas package _08lambdas fun Lock.locked(compute: () -> T): T { this.lock() try { return compute() } finally { this.unlock() } }

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Delegation package _09delegation class MyList(val l: List) : List by l fun main(args: Array) { val list = MyList(listOf("a, b, c")) list.forEach { println(it) } }

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Delegation package _09delegation class LazyString { val value: String by Delegates.lazy { println("heavy computation") "the string!" } }

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Builders & DSL support package _10builders fun data(build: Data.() -> Unit): Data { val result = Data() result.build() return result }