Differences

This shows you the differences between two versions of the page.

--- programmiersprachen:scala [2015/10/10 16:40] – angelegt phreazer
+++ programming_languages:scala [2017/02/19 15:46] (current) – ↷ Seite von programmiersprachen:scala nach programming_languages:scala verschoben phreazer
@@ Line 1: / Line 1: @@
-Scala
+====== Scala ======
+**Sca**lable **la**nguage
+===== Start =====
-====== Start ======
   * No primitive types, everything is an object
+  * No semicolon
+  * Object is a singleton
+  * Methods can be defined private or protected. If no modifer is given, method is public.
+  * No static methods
-===== Hello World =====
+==== Hello World ====
 <code scala>
-    object HelloWorld {
+object HelloWorld {
-      def main(args: Array[String]) {
+  def main(args: Array[String]) {
-        println("Hello, world!")
+    println("Hello, world!")
-      }
+  }
-<code>
+}
-    }
+</code>
+===== Control structures =====
+if/else-Constructs have a return value
+==== for loop ====
+<code scala>
+for (i <- 1 to 10) println(i)
+</code>
+<code scala>
+// different steps
+for (i <- 4 to (17,3)) println(i)
+// other data types than int
+for (s <- myList) println(s)
+// multiple generators
+for (i <- 0 to 2; j <- 3 to 4) println(i+" "+j)
+// filter
+    for {i <- 1 to 6
+         j <- 1 to 6
+         if (i % 2 == 0)
+         if (j % 2 != 0)} println(i+" "+j)
+// yield
+    val list: List[Int] = List(1,2,3,4)
+    val result = for (i <- list) yield i * 2
+    println(result)
+</code>
+==== match ====
+Implizites break
+<code scala>
+val iValue = 3
+iValue match{
+  case 1 => println("one")
+  case _ => println("empty")
+}
+</code>
+===== Singleton objects =====
+There are no static methods/vars in scala and singleton objects can't be constructed using a constructor with new.
+<code scala>
+object ScalaObject {
+  val b = 5
+  def test(a: Double) : Double = {
+.* + b
+  }
+}
+</code>
+===== Companion object =====
+Prerequisite: object and class have the same name and are defined in the same file. Companion objects can access their private variables. Singleton objects without companion clases are standalone objects.
+===== Case classes =====
+  * Use a factory method for construction
+  * All passed parameters are a val-variable of the class
+  * Can be used for pattern matching
+  * Implement toString, hashCode, equals and have a copy method
+<code scala>
+case class Person (firstName : String, lastName : String, age : Int){
+  def isAdult : Boolean = if (age >= 18) true else false
+}
+</code>
+===== Inheritance =====
+Scala doesn't support multiple inheritance.
+class B(arg:Int) extends A {}
+Functions can be overridden with overide before func definition.
+Overridding classes, functions or variables can be forbidden with prefix final.
+==== Abstract classes ====
+Difference to Traits: Abstract classes can have constructors. A class which inherits from an abstract class can't inherit from another.
+The usage of override is optional.
+==== Packages object ====
+Objects which are visible in a whole package.
+===== Identity and equality =====
+==-Operator checks equality (identity in Java)
+eq-Operator checks identity
+eq and ne are only defined for clases of type scala.AnyRef.
+===== Learning sources =====
+http://www.scalatutorial.de/topic143.html