Programozás | Java, JSP » Háber János - Scala, A Java jövője

Scala A Java jövője Háber János Scala > Java? - JVM-en fut - Típusos - Teljesen objektum orientált - Funkcionális programozás támogatása - Minta illesztés - Többszörös öröklődés (Mixin) - Implicit konverzió - Actor alapú konkurencia kezelés - Ruby szerű szintaxis és még sok minden Scala + Java - Egyszerre használható Java és Scala ugyanabban a projektben - Használhatók a meglévő Java libek - IDE támogatás - Ha valami nem megy, csináld Jávában Teljesen Objektum orientált //Minden érték egy objektum 1.toString //Minden művelet egy metódus hívás 1 + 2 + 3 -> (1).+(2)+(3) // . és ( ) elhagyható "abc" charAt 1 -> "abc".charAt(1) Hello World //Java public class HelloWorld { public static void main(String[] args) { String message = "Hello World"; System.outprintln(message); } } //Scala object HelloWorld { def main(args:Array[String]):Unit = { val message = "Hello World"

println(message) } } Singleton támogatás object Hello { def world = "Hello World" } Hello.world //Hello$.class import scala.ScalaObject; public final class Hello$ implements ScalaObject { private Hello$() { MODULE$ = this; } public String world() { return "Hello World"; } public static final MODULE$; static { new (); } } //Hello.class import scala.reflectScalaSignature; @ScalaSignature(bytes=".removed") public final class Hello { public static final String world() { return Hello.MODULE$world(); } } Automatikus getter/setter class SimpleVal { val finalValue: String = "hi" var simpleVariable: String = "" } import scala.ScalaObject; import scala.reflectScalaSignature; @ScalaSignature(bytes = ".removed") public class SimpleVal implements ScalaObject { private final String finalValue = "hi"; private String simpleVariable = ""; public String finalValue() { return this.finalValue; } public String

simpleVariable() { return this.simpleVariable; } public void simpleVariable $eq(String paramString) { this.simpleVariable = paramString; } } Scala - tömör //Java public class Person { private final String name; private final int age; public Person(String name,int age) { this.name = name; this.age = age; } public String getName() { return name; } public int getAge() { return age; } } //Scala class Person(val name:String, val age:Int) Scala - tömör //Java //Scala public class Person { private String name; private int age; public Person(String name,int age) { this.name = name; this.age = age; } import reflect.BeanProperty public String getName() { return name; } public int setName(String name) { this.name=name; } public String getAge() { return age; } public int setAge(String age) { this.age=age; } } class Person { @BeanProperty var name: String = @BeanProperty var age: Int = } Típus következtetés val sum = 1 + 2 + 3 val nums = List(1, 2, 3) val map =

Map("abc" -> List(1, 2, 3)) val sum: Int = 1 + 2 + 3 val nums: List[Int] = List(1, 2, 3) val map: Map[String, List[Int]] = Map("abc" -> List(1, 2, 3)) Duck typing object BigDuck { def quack(value: String) = { value.toUpperCase } } object SmallDuck { def quack(value: String) = { value.toLowerCase } } object IamNotReallyADuck { def quack(value: String) = { "prrrrrp" } } def quacker(duck: {def quack(value: String): String}) { println (duck.quack("Quack")) } quacker(BigDuck) quacker(SmallDuck) quacker(IamNotReallyADuck) class MyDao[T <: {def id : K}, K] High-order funkciók def transaction(function: => Any): Any = { //. } transaction { //here your database code } High-order funkciók def measure[T](func: => T):T = { val start = System.nanoTime() val result = func val elapsed = System.nanoTime() - start println("The execution of this call took: %s ns".format(elapsed)) result } def myCallback = {

Thread.sleep(1000) "Im a callback" } val result = measure(myCallback) > The execution of this call took: 1002449000 ns High-order funkciók import org.scalatestFunSuite import scala.collectionmutableStack class ExampleSuite extends FunSuite { test("pop is invoked on an empty stack") { val emptyStack = new Stack[Int] intercept[NoSuchElementException] { emptyStack.pop() } assert(emptyStack.isEmpty) } } Scala - minta illesztés - Hasonló a Java switch-hez - Bármilyen típusú adatra használható - Első találat szabály def matchTest(x: Any): Any = x match { case 1 | 2 | 3 => "one" case "two" => 2 case a: Int if (a > 100) => a - 3 case b: Int => b + 3 case => "None of above" } Option def div(a:Int)(b:Int):Option[Int] = if (b <= 0) None else if (a < b) Some(0) else Some(1 + div(a - b)(b).get) div(25)(5) // => Some(5) div(150)(2) // => Some(75) div(13)(4) // => Some(3) div(13)(0)

div(25)(-5) // => None // => None div(13)(0) match { case Some(x) => println(x) case None => println("Problems") } // => prints "Problems" div(25)(5) match { case Some(x) => println(x) case None => println("Problems") } // => prints "5" Implicit konverzió implicit def doubleToInt(d: Double) = d.toInt val x: Int = 42.0 //Java public <T> void javaNoManifest(Class<T> clazz) { //. } //Scala def manifestTest[T](implicit m:Manifest[T]) = { m.runtimeClass } Operátor túlterhelés class Complex(val real : Double, val imag : Double) { def +(that: Complex) = new Complex(this.real + thatreal, thisimag + thatimag) def -(that: Complex) = new Complex(this.real - thatreal, thisimag - thatimag) override def toString = real + " + " + imag + "i" } object Complex { def main(args : Array[String]) : Unit = { var a = new Complex(4.0,50) var b = new Complex(2.0,30) println(a) // 4.0 + 50i println(a

+ b) // 6.0 + 80i println(a - b) // 2.0 + 20i } } Trait-ek //Hasonló a Java interfacehez trait Language { val name:String //De tartalmazhat implementációt is override def toString = name } Trait-ek trait JVM { override def toString = super.toString + " runs on JVM" } trait Static { override def toString = super.toString + " is Static" } //A trait-ek összefűzhetők (a sorrend számít!) class Scala extends Language with JVM with Static { val name="Scala" } println(new Scala()) // -> "Scala runs on JVM is Static" Trait-ek trait Quacking { def quack() = { println("Quack quack quack!") } } class Duck { val version = "ACME Inc. Generic Duck v10" } val aDuck = new Duck with Quacking aDuck.quack() Case Class abstract class Term case class Var(name: String) extends Term case class Fun(arg: String, body: Term) extends Term case class App(f: Term, v: Term) extends Term def printTerm(term: Term) { term match

{ case Var(n) => print(n) val x1 = Var("x") val x2 = Var("x") val y1 = Var("y") println("" + x1 + " == " + x2 + " => " + (x1 == x2)) println("" + x1 + " == " + y1 + " => " + (x1 == y1)) case Fun(x, b) => print("^" + x + ".") printTerm(b) case App(f, v) => Console.print("(") printTerm(f) print(" ") printTerm(v) print(")") Var(x) == Var(x) => true Var(x) == Var(y) => false } } Scala Java Interoperability class Companion { def hello() { println("Hello (class)") } // [1] } object Companion { def hallo() { println("Hallo (object)") } // [2] def hello() { println("Hello (object)") } // [3] } public class TestCompanion { public static void main(String[] args) { new Companion().hello(); // [1] Companion.hallo(); // [2] (static) Companion$.MODULE$hello(); // [3] (static) } } Multiline String

és Beágyazott XML val someXMLInAString = """ <sammich> <bread>wheat</bread> <meat>salami</meat> <condiments> <condiment expired="true">mayo</condiment> <condiment expired="false">mustard</condiment> </condiments> </sammich> """ import scala.xml val someXML = <sammich> <bread>wheat</bread> <meat>salami</meat> <condiments> <condiment expired="true">mayo</condiment> <condiment expired="false">mustard</condiment> </condiments> </sammich> Információk http://www.scala-langorg/ https://www.courseraorg/course/progfun http://blog.knolduscom http://java.dzonecom/taxonomy/term/277/0 http://www.scala-lang org/docu/files/ScalaByExample.pdf http://www.slidesharenet/tpunder/a-briefintro-to-scala http://cscarioni.blogspotie/2013/02/ducktyping-in-scala-kind-of-structuralhtml

Köszönöm a figyelmet Elérhetőség: janos.haber@finesolutionhu