Scala

Andreas Enbohm 2009-03-15 Scala or ” The Free Lunch is Over”

Why Scala ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Scala - Features ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],def sum(a:Int,b:Int) = a+b

Scala – Compared to Java ,[object Object],[object Object],class Person (var firstName: String, var lastName: String) { } public class Person { private String firstName; private String lastName; public Person(String firstName, String lastName) { this .firstName = firstName; this .lastName = lastName; } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this .firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this .lastName = lastName; } }

Scala – Compared to Java ,[object Object],[object Object],[object Object],[object Object],[object Object],val myInt: Int = 1; val anotherInt = 2 val anObject = Object //Omit () if you want just ’cluttering’ your code val aList = List(”John Doe”, ”Jane Doe”, ”Baby Doe”) println ("Hi, " +aList.tail.head) //Prints “Hi, Jane Doe” List<String> aList = new ArrayList<String>(); //Java syntax for creating a list-object val aList = List //Scala syntax for creating corresponding list val aList = List[String] //Also works, notice just ONE generic definiton import java.util.{Date,Locale} import java.text.DateFormat import java.text.DateFormat._ val now = new Date val df = getDateInstance(LONG, Locale.FRANCE) println ( df format now) //same as df.format(now)

Scala – Compared to Java ,[object Object],[object Object],[object Object],try { doSomething(params) } catch { case ex: IOException => println("Oops! Some file is probably missing") case ex: NullPointerException => println(“Dohh!! Must initialize the variable ") } object MatchTest1 extends Application { def matchTest(x: Int): String = x match { case 1 => "one" case 2 => "two" case _ => "many" } println (matchTest(1)) //Prints “one” println (matchTest(99)) //Prints “many” }

Duck Typing in Scala ,[object Object],[object Object],[object Object],[object Object],class Duck { public void quack() { print(”Duck Quacking!”) } class Person { public void quack() { print(”Person Quacking!”) } } Duck d = new Duck(); Person p = new Person(); testQuack(d); testQucak(p); testQuack(duckableObject) { duckableObject.quack(); //Lets hope this work!!! }

Duck Typing in Scala ,[object Object],[object Object],[object Object],[object Object],[object Object],class File (name: String) { def getName(): String = name def open() { /*..*/ } def close() { println("close file") } } def testPrintName (aFileObject: { def getName(): String }) { println (aFileObject.getName) } testPrintName (new File("test.txt")) testPrintName (new java.io.File("test.txt")) trait HasName { def getName() : String } def testPrintName (HasName f) = { println(f.getName) }

Actors ,[object Object],[object Object],[object Object],[object Object]

Downsides ,[object Object],[object Object],[object Object]

Scala

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