2.1 Recap From Day One

Variables Scala: val s = “Hello World” var i = 1 Java: public final String s = “Hello World”; public int i = 1;

Methods Scala: def add(x: Int, y: Int): Int = { x + y } def add(x: Int, y: Int) = x + y def doSomething(text: String) { } Java: public int add(int x, int y) { return x + y; } public void doSometing(String text) { }

Classes and constructors Scala: class Person(val name: String) Java: public class Person { private final String name; public Person(String name) { this.name = name; } public String getName() { return name; } }

Tuples Scala: val tuple: Tuple2[Int, String] = (1, “apple”) val quadruple = (2, “orange”, 0.5d, false) Java: Pair<Integer, String> tuple = new Pair<Integer, String>(1, “apple”) ... yeah right... ;-)

The Option type val someOption : Option [ String ] = Some ( "value" ) val noOption : Option [ String ] = None

First class funtions val numbers = List(1, 2, 3, 4, 5) numbers.filter(i => i > 2) // List(3, 4, 5)

Closures val people = List(Person(“Alf”), Person(“Fredrik”)) val name = “Fredrik” people.filter(_.name == name ) // Person(“ Fredrik”)

val myObject = ... val res = myObject match { case i : Int if i == 1 => "Found an int which is 1" case s : String => "Found a String" case other => error ( "Unknown " + other ) } Pattern matching

Traits trait Ordered[A] { def compare(that: A): Int def < (that: A): Boolean = ( this compare that) < 0 def > (that: A): Boolean = ( this compare that) > 0 def <= (that: A): Boolean = ( this compare that) <= 0 def >= (that: A): Boolean = ( this compare that) >= 0 }

Todays schedule Higher order functions

2.1 Recap From Day One

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2.1 Recap From Day One