Scala example source code file (switch.scala)

This example Scala source code file (switch.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

a, a, b, b, c, c, c1, c2, c3, c4, char, char, int, p

The Scala switch.scala source code

import scala.annotation.switch

// this is testing not so much how things ought to be but how they are;
// the test is supposed to start failing if the behavior changes at all.
object Other {
  val C1 = 'P'                // fails: not final
  final val C2 = 'Q'          // succeeds: singleton type Char('Q') inferred
  final val C3: Char = 'R'    // fails: type Char specified
  final val C4 = '\u000A'     // succeeds like C2 but more unicodey
}

object Main {
  def succ1(c: Char) = (c: @switch) match {
    case 'A' | 'B' | 'C'  => true
    case 'd'              => true
    case 'f' | 'g'        => true
    case _                => false
  }
  
  def succ2(c: Char) = (c: @switch) match {
    case 'A' | 'B' | 'C'  => true
    case Other.C2         => true
    case Other.C4         => true
    case _                => false
  }
  
  // has a guard
  def fail1(c: Char) = (c: @switch) match {
    case 'A' | 'B' | 'C'  => true
    case x if x == 'A'    => true
    case _                => false
  }
  
  // throwing in @unchecked on the next two to make sure
  // multiple annotations are processed correctly
  
  // thinks a val in an object is constant... so naive
  def fail2(c: Char) = (c: @switch @unchecked) match {
    case 'A'        => true
    case Other.C1   => true
    case _          => false
  }
  
  // more naivete
  def fail3(c: Char) = (c: @unchecked @switch) match {
    case 'A'        => true
    case Other.C3   => true
    case _          => false
  }
  
  // guard case done correctly
  def succ3(c: Char) = (c: @switch) match {
    case 'A' | 'B' | 'C'  => true
    case x                => x == 'A'
  }
  
  // some ints just to mix it up a bit
  def succ4(x: Int, y: Int) = ((x+y): @switch) match {
    case  1 => 5
    case  2 => 10
    case  3 => 20
    case  4 => 50
    case 5|6|7|8 => 100
    case _  => -1
  }    
}