Code Examples for

Programming in Scala, Second Edition

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27 Annotations

Sample run of chapter's interpreter examples

27.1 Why have annotations?

27.2 Syntax of annotations

// In file annotations/Deprecation1.scala @deprecated def bigMistake() = //...
// In file annotations/Misc.scala @deprecated class QuickAndDirty { //... }
// In file annotations/Misc.scala (e: @unchecked) match { // non-exhaustive cases... }
@cool val normal = "Hello" @coolerThan(normal) val fonzy = "Heeyyy"
scala> import annotation._ import annotation._ scala> class strategy(arg: Annotation) extends Annotation defined class strategy scala> class delayed extends Annotation defined class delayed scala> @strategy(@delayed) def f(){} <console>:1: error: illegal start of simple expression @strategy(@delayed) def f(){} ^ scala> @strategy(new delayed) def f(){} f: ()Unit

27.3 Standard annotations

@deprecated def bigMistake() = //...
// In file annotations/Deprecation2.scala @deprecated("use newShinyMethod() instead") def bigMistake() = //...
$ scalac -deprecation Deprecation2.scala Deprecation2.scala:33: warning: method bigMistake in object Deprecation2 is deprecated: use newShinyMethod() instead bigMistake() ^ one warning found
// In file annotations/Native.scala @native def beginCountdown() { }

27.4 Conclusion

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