Scala and Lift presentation
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Scala is a statically typed programming language for the Java Virtual Machine that aims to be concise, object-oriented, and functional. Some key features of Scala include type inference, pattern matching, actors for concurrency, and compiling to Java bytecode. Scala improves on Java by handling null values safely by default and providing more concise syntax for working with collections, XML, and other common tasks. Scala is growing in popularity as a potential successor to Java due to its interoperability while improving on Java in several ways.
![Scala - Basicsclass Test {// variable definitionvar n = 5// value definitionval i = 10// function definitiondef printit(x: Any) = println(x)def sum(i: Int, n: Int) = i+n}object Test extends Test {def main(args: Array[String]): Unit = { printit(sum(i,n)) }}](https://image.slidesharecdn.com/liftjavarsovia-12802220312072-phpapp01/85/Scala-and-Lift-presentation-13-320.jpg)
![Working with arraysJavapublicclass Partition {Person[] all;Person[] adults;Person[] minors; { ArrayList<Person> minorsList = new ArrayList<Person>();ArrayList<Person> adultsList = new ArrayList<Person>();for(int i=0; i<all.length; i++ ) { (all[i].age<18 ? adultsList: minorsList).add(all[i]); } minors = (Person[]) minorsList.toArray(); adults = (Person[]) adultsList.toArray();}}](https://image.slidesharecdn.com/liftjavarsovia-12802220312072-phpapp01/85/Scala-and-Lift-presentation-16-320.jpg)
![Working with arraysScalaval all: Array[Person]val (minors, adults) = all.partition(_.age<18)](https://image.slidesharecdn.com/liftjavarsovia-12802220312072-phpapp01/85/Scala-and-Lift-presentation-17-320.jpg)
![Null’s - Scala val capitals = Map("Poland" -> "Warsaw");val capitalOption: Option[String] = capitals.get("Polska") capitalOption match {case Some(value) => println(value)case None => println("Not found")case _ => }if(capitalOption.isDefined) println(capitalOption.get) println(capitalOption getOrElse "Not found")](https://image.slidesharecdn.com/liftjavarsovia-12802220312072-phpapp01/85/Scala-and-Lift-presentation-19-320.jpg)
![Actorsclass ActorUser {def send(msg: Any) = ScalaActor ! msg}object ScalaActor extends Actor { /* The $actor's mailbox. */// private[actors] val mailbox = new MQueue[Msg]("Reactor") def act() { receive { case"ping!" => println("pinged!");case ("ping!", actor: Actor) => actor ! "pong!" case msg => println("unhandled message type:"+msg) } }}](https://image.slidesharecdn.com/liftjavarsovia-12802220312072-phpapp01/85/Scala-and-Lift-presentation-23-320.jpg)
Scala and Lift presentation
- 2. Scala the next Java ?Łukasz Kuczera
- 3. ScalaStatically typed with types inferentionObject-functionalCompiles to Java bytecodeAnd CLI .Net
- 5. Pizza
- 8. ScalaType InferenceUniform Access PrincipleClosuresHigher Order FunctionsPattern MatchingActorsGenericsNative XML supportAbstract control structuresImplicit conversions and parametersAdvanced for expressionsAnnotationsCombinator parsingTraitsDuck typingNull „safety”
- 9. „If I where to choose language other thanJava it would be Scala”
- 10. „I can honestly say if someone had shown me the Programming in Scala book by Martin Odersky, Lex Spoon & Bill Venners back in 2003 I'd probably have never created Groovy”
- 11. „Scala, it must be stated, is the current heir apparent to the Java throne. No other language on the JVM seems as capable of being a "replacement for Java" as Scala, and the momentum behind Scala is now unquestionable”
- 13. Scala - Basicsclass Test {// variable definitionvar n = 5// value definitionval i = 10// function definitiondef printit(x: Any) = println(x)def sum(i: Int, n: Int) = i+n}object Test extends Test {def main(args: Array[String]): Unit = { printit(sum(i,n)) }}
- 14. Class Parameters - Javapublicclass Person { private String name; privateintage;publicPerson(String name, int age) { this.name = name; this.age = age; } public String getName() { returnname; } publicvoid setName(String name) { this.name = name; } publicint getAge() { returnage; } publicvoid setAge(int age) { this.age = age; }}
- 15. Class Parameters - ScalaclassPerson(var name: String, var age: Int)
- 16. Working with arraysJavapublicclass Partition {Person[] all;Person[] adults;Person[] minors; { ArrayList<Person> minorsList = new ArrayList<Person>();ArrayList<Person> adultsList = new ArrayList<Person>();for(int i=0; i<all.length; i++ ) { (all[i].age<18 ? adultsList: minorsList).add(all[i]); } minors = (Person[]) minorsList.toArray(); adults = (Person[]) adultsList.toArray();}}
- 17. Working with arraysScalaval all: Array[Person]val (minors, adults) = all.partition(_.age<18)
- 18. Null’s – JavaMap<String, String> capitals = newHashMap<String, String>();capitals.put("Poland", "Warsaw");System.out.println(capitals.get("Polska").trim());Exception in thread "main" java.lang.NullPointerException
- 19. Null’s - Scala val capitals = Map("Poland" -> "Warsaw");val capitalOption: Option[String] = capitals.get("Polska") capitalOption match {case Some(value) => println(value)case None => println("Not found")case _ => }if(capitalOption.isDefined) println(capitalOption.get) println(capitalOption getOrElse "Not found")
- 20. XMLval xml = <a href="http://example.com"> <customTagb="foo"> <deepTagb="bar" />Custom content </customTag> </a>println(xml \ "customTag")println(xml \\ "deepTag")println(xml \\ "@b")println(xml \ "customTag" \ "deepTag" \ "@b")Outputs:<customTag b="foo"><deepTag b="bar"></deepTag>Custom content</customTag><deepTag b="bar"></deepTag>foobarbar
- 21. XMLval xml =<divclass="rsswidget"><ul><liclass="rsswidgettitle"><ahref="http://www.quotationspage.com/qotd.html">Quotes of the Day</a></li><liclass="rsswidgetitem"><ahref="http://www.quotationspage.com/quotes/C._P._Snow">C. P. Snow</a></li><liclass="rsswidgetitem"><ahref="http://www.quotationspage.com/quotes/unknown">unknown</a></li><liclass="rsswidgetitem"><ahref="http://www.quotationspage.com/quotes/Frederick">Frederick</a></li></ul> ...</div>(xml \\ "@href").slice(1,4).foreach(url => println("URL:"+url)val con = new URL(url.toString).openConnectionval reader = newBufferedReader(newInputStreamReader(con.getInputStream, "ISO-8859-1"))var line = "";while(line != null) { line = reader.readLineif(line != null) println(line) } con.getInputStream.close)
- 22. ActorsEasier concurrencyMessage passing instead of locksAsynchronusImplemented using Java threadsScalaActors, Akka, Lift - CometActor
- 23. Actorsclass ActorUser {def send(msg: Any) = ScalaActor ! msg}object ScalaActor extends Actor { /* The $actor's mailbox. */// private[actors] val mailbox = new MQueue[Msg]("Reactor") def act() { receive { case"ping!" => println("pinged!");case ("ping!", actor: Actor) => actor ! "pong!" case msg => println("unhandled message type:"+msg) } }}
- 24. GuiceMinimize mutabilityAvoid static state@NullableJSR 308 - @NonNull
- 25. LiftChat Application Using Comet
- 28. HTTP GET
- 29. Ajax
- 30. Comet
- 32. Linkshttp://days2010.scala-lang.org/node/136 - lots of Scala videoshttp://twit.tv/floss125 - Lifts Creator interviewhttp://www.youtube.com/watch?v=01rXrI6xelE – Scala creator speak at Google tech talks
- 33. Thank YouQ&A