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BAEL-3533 - Scala Pattern Matching (Switch/Case) (eugenp#8226)
* BAEL-3533 Scala Pattern Matching (Switch/Case) * BAEL-3533 Scala Pattern Matching (Switch/Case) * BAEL-3533 Scala Pattern Matching (Switch/Case) * BAEL-3533 Scala Pattern Matching (Switch/Case) * BAEL-3533 Scala Pattern Matching (Switch/Case) * BAEL-3533 Scala Pattern Matching (Switch/Case) * BAEL-3533 Scala Pattern Matching (Switch/Case) * BAEL-3533 Scala Pattern Matching (Switch/Case) * BAEL-3533 Scala Pattern Matching (Switch/Case) * BAEL-3533 Scala Pattern Matching (Switch/Case)
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‎core-scala/src/main/scala/com/baeldung/scala/PatternMatching.scala

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package com.baeldung.scala
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// Case Class
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abstract class Animal
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case class Mammal(name: String, fromSea: Boolean) extends Animal
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case class Bird(name: String) extends Animal
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case class Fish(name: String) extends Animal
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// Sealed Class
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sealed abstract class CardSuit
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case class Spike() extends CardSuit
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case class Diamond() extends CardSuit
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case class Heart() extends CardSuit
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case class Club() extends CardSuit
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object Person {
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def apply(fullName: String) = fullName
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def unapply(fullName: String): Option[String] = {
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if (!fullName.isEmpty)
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Some(fullName.replaceAll("(?<=\\w)(\\w+)", "."))
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else
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None
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}
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}
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class PatternMatching {
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def caseClassesPatternMatching(animal: Animal): String = {
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animal match {
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case Mammal(name, fromSea) => s"I'm a $name, a kind of mammal. Am I from the sea? $fromSea"
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case Bird(name) => s"I'm a $name, a kind of bird"
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case _ => "I'm an unknown animal"
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}
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}
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def constantsPatternMatching(constant: Any): String = {
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constant match {
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case 0 => "I'm equal to zero"
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case 4.5d => "I'm a double"
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case false => "I'm the contrary of true"
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case _ => s"I'm unknown and equal to $constant"
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}
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}
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def sequencesPatternMatching(sequence: Any): String = {
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sequence match {
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case List(singleElement) => s"I'm a list with one element: $singleElement"
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case List(_, _*) => s"I'm a list with one or multiple elements: $sequence"
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case Vector(1, 2, _*) => s"I'm a vector: $sequence"
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case _ => s"I'm an unrecognized sequence. My value: $sequence"
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}
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}
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def tuplesPatternMatching(tuple: Any): String = {
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tuple match {
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case (first, second) => s"I'm a tuple with two elements: $first & $second"
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case (first, second, third) => s"I'm a tuple with three elements: $first & $second & $third"
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case _ => s"Unrecognized pattern. My value: $tuple"
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}
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}
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def typedPatternMatching(any: Any): String = {
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any match {
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case string: String => s"I'm a string. My value: $string"
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case integer: Int => s"I'm an integer. My value: $integer"
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case _ => s"I'm from an unknown type. My value: $any"
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}
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}
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def regexPatterns(toMatch: String): String = {
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val numeric = """([0-9]+)""".r
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val alphabetic = """([a-zA-Z]+)""".r
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val alphanumeric = """([a-zA-Z0-9]+)""".r
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toMatch match {
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case numeric(value) => s"I'm a numeric with value $value"
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case alphabetic(value) => s"I'm an alphabetic with value $value"
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case alphanumeric(value) => s"I'm an alphanumeric with value $value"
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case _ => s"I contain other characters than alphanumerics. My value $toMatch"
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}
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}
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def optionsPatternMatching(option: Option[String]): String = {
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option match {
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case Some(value) => s"I'm not an empty option. Value $value"
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case None => "I'm an empty option"
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}
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}
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def patternGuards(toMatch: Any, maxLength: Int): String = {
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toMatch match {
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case list: List[Any] if (list.size <= maxLength) => "List is of acceptable size"
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case list: List[Any] => "List has not an acceptable size"
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case string: String if (string.length <= maxLength) => "String is of acceptable size"
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case string: String => "String has not an acceptable size"
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case _ => "Input is neither a List or a String"
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}
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}
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def sealedClass(cardSuit: CardSuit): String = {
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cardSuit match {
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case Spike() => "Card is spike"
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case Club() => "Card is club"
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case Heart() => "Card is heart"
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case Diamond() => "Card is diamond"
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}
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}
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def extractors(person: Any): String = {
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person match {
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case Person(initials) => s"My initials are $initials"
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case _ => "Could not extract initials"
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}
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}
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def closuresPatternMatching(list: List[Any]): List[Any] = {
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list.collect { case i: Int if (i < 10) => i }
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}
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def catchBlocksPatternMatching(exception: Exception): String = {
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try {
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throw exception
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} catch {
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case ex: IllegalArgumentException => "It's an IllegalArgumentException"
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case ex: RuntimeException => "It's a RuntimeException"
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case _ => "It's an unknown kind of exception"
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}
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}
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}

‎core-scala/src/test/scala/com/baeldung/scala/PatternMatchingUnitTest.scala

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package com.baeldung.scala
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import java.io.FileNotFoundException
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import org.junit.Assert.assertEquals
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import org.junit.Test
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class PatternMatchingUnitTest {
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@Test
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def whenAMammalIsGivenToTheMatchExpression_ThenItsRecognizedAsMammal(): Unit = {
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val result = new PatternMatching().caseClassesPatternMatching(Mammal("Lion", fromSea = false))
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assertEquals("I'm a Lion, a kind of mammal. Am I from the sea? false", result)
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}
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@Test
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def whenABirdIsGivenToTheMatchExpression_ThenItsRecognizedAsBird(): Unit = {
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val result = new PatternMatching().caseClassesPatternMatching(Bird("Pigeon"))
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assertEquals("I'm a Pigeon, a kind of bird", result)
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}
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@Test
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def whenAnUnkownAnimalIsGivenToTheMatchExpression_TheDefaultClauseIsUsed(): Unit = {
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val result = new PatternMatching().caseClassesPatternMatching(Fish("Tuna"))
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assertEquals("I'm an unknown animal", result)
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}
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@Test
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def whenTheConstantZeroIsPassed_ThenItMatchesTheCorrespondingPattern(): Unit = {
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val result = new PatternMatching().constantsPatternMatching(0)
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assertEquals("I'm equal to zero", result)
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}
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@Test
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def whenFourAndAHalfIsPassed_ThenItMatchesTheCorrespondingPattern(): Unit = {
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val result = new PatternMatching().constantsPatternMatching(4.5d)
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assertEquals("I'm a double", result)
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}
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@Test
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def whenTheBooleanFalseIsPassed_ThenItMatchesTheCorrespondingPattern(): Unit = {
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val result = new PatternMatching().constantsPatternMatching(false)
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assertEquals("I'm the contrary of true", result)
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}
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@Test
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def whenAnUnkownConstantIsPassed_ThenTheDefaultPatternIsUsed(): Unit = {
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val result = new PatternMatching().constantsPatternMatching(true)
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assertEquals("I'm unknown and equal to true", result)
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}
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@Test
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def whenASingleElementListIsPassed_ThenItMatchesTheCorrespondingPattern(): Unit = {
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val result = new PatternMatching().sequencesPatternMatching(List("String"))
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assertEquals("I'm a list with one element: String", result)
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}
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@Test
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def whenAMultipleElementsListIsPassed_ThenItMatchesTheCorrespondingPattern(): Unit = {
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val result = new PatternMatching().sequencesPatternMatching(List("Multiple", "Elements"))
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assertEquals("I'm a list with one or multiple elements: List(Multiple, Elements)", result)
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}
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@Test
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def whenAVectorBeginningWithOneAndTwoIsPassed_ThenItMatchesTheCorrespondingPattern(): Unit = {
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val result = new PatternMatching().sequencesPatternMatching(Vector(1, 2, 3))
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assertEquals("I'm a vector: Vector(1, 2, 3)", result)
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}
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@Test
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def whenANotMatchingVectorIsPassed_ThenItShouldntMatchAndEnterTheDefaultClause(): Unit = {
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val result = new PatternMatching().sequencesPatternMatching(Vector(2, 1))
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assertEquals("I'm an unrecognized sequence. My value: Vector(2, 1)", result)
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}
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@Test
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def whenAnEmptyListIsPassed_ThenItShouldntMatchAndEnterTheDefaultClause(): Unit = {
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val result = new PatternMatching().sequencesPatternMatching(List())
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assertEquals("I'm an unrecognized sequence. My value: List()", result)
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}
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@Test
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def whenATwoElementsTupleIsPassed_ThenItMatchesTheCorrespondingPattern(): Unit = {
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val result = new PatternMatching().tuplesPatternMatching(("First", "Second"))
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assertEquals("I'm a tuple with two elements: First & Second", result)
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}
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@Test
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def whenAThreeElementsTupleIsPassed_ThenItMatchesTheCorrespondingPattern(): Unit = {
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val result = new PatternMatching().tuplesPatternMatching(("First", "Second", "Third"))
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assertEquals("I'm a tuple with three elements: First & Second & Third", result)
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}
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@Test
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def whenAnoterKindOfTupleIsPassed_ThenItShouldntMatchAndReturnTheDefaultPattern(): Unit = {
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val result = new PatternMatching().tuplesPatternMatching(("First"))
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assertEquals("Unrecognized pattern. My value: First", result)
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}
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@Test
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def whenAStringConsistingOfNumericsOnlyIsPassed_ThenItShouldMatchTheNumericRegex(): Unit = {
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val result = new PatternMatching().regexPatterns("123")
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assertEquals("I'm a numeric with value 123", result)
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}
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@Test
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def whenAStringConsistignOfAlphabeticsOnlyIsPassed_ThenItShouldMatchTheAlphabeticRegex(): Unit = {
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val result = new PatternMatching().regexPatterns("abc")
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assertEquals("I'm an alphabetic with value abc", result)
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}
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@Test
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def whenAStringConsistignOfAlphanumericsOnlyIsPassed_ThenItShouldMatchTheAlphanumericRegex(): Unit = {
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val result = new PatternMatching().regexPatterns("abc123")
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assertEquals("I'm an alphanumeric with value abc123", result)
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}
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@Test
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def whenAnotherTypeOfStringIsPassed_ThenItShouldntMatchAndReturnTheDefaultPattern(): Unit = {
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val result = new PatternMatching().regexPatterns("abc_123")
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assertEquals("I contain other characters than alphanumerics. My value abc_123", result)
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}
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@Test
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def whenAFilledOptionIsPassed_ThenItShouldMatchTheSomeClause(): Unit = {
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val result = new PatternMatching().optionsPatternMatching(Option.apply("something"))
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assertEquals("I'm not an empty option. Value something", result)
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}
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@Test
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def whenAnEmptyOptionIsPassed_ThenItShouldMatchTheNoneClause(): Unit = {
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val result = new PatternMatching().optionsPatternMatching(Option.empty)
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assertEquals("I'm an empty option", result)
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}
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@Test
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def whenAListWithAcceptedSizeIsPassed_ThenThePositiveMessageIsSent(): Unit = {
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val result = new PatternMatching().patternGuards(List(1, 2), 3)
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assertEquals("List is of acceptable size", result)
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}
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@Test
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def whenAListWithAnUnacceptedSizeIsPassed_ThenTheNegativeMessageIsSent(): Unit = {
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val result = new PatternMatching().patternGuards(List(1, 2, 3, 4), 3)
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assertEquals("List has not an acceptable size", result)
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}
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@Test
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def whenAStringWithAcceptedSizeIsPassed_ThenThePositiveMessageIsSent(): Unit = {
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val result = new PatternMatching().patternGuards("OK", 3)
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assertEquals("String is of acceptable size", result)
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}
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@Test
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def whenAStringWithAnUnacceptedSizeIsPassed_ThenTheNegativeMessageIsSent(): Unit = {
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val result = new PatternMatching().patternGuards("Not OK", 3)
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assertEquals("String has not an acceptable size", result)
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}
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@Test
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def whenAnObjectWhichIsNotAListOrAStringIsPassed_thenTheDefaultClauseIsUsed(): Unit = {
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val result = new PatternMatching().patternGuards(1, 1)
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assertEquals("Input is neither a List or a String", result)
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}
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@Test
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def whenACardSuitIsPassed_ThenTheCorrespondingMatchCaseClauseIsUsed(): Unit = {
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assertEquals("Card is spike", new PatternMatching().sealedClass(Spike()))
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assertEquals("Card is club", new PatternMatching().sealedClass(Club()))
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assertEquals("Card is heart", new PatternMatching().sealedClass(Heart()))
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assertEquals("Card is diamond", new PatternMatching().sealedClass(Diamond()))
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}
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@Test
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def whenAnObjectWithExtractorIsPassed_ThenTheExtractedValueIsUsedInTheCaseClause(): Unit = {
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val person = Person("John Smith")
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val result = new PatternMatching().extractors(person)
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assertEquals("My initials are J. S.", result)
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}
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@Test
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def whenAnObjectWithExtractorIsPassed_AndTheValueIsEmpty_ThenTheDefaultCaseClauseIsUsed(): Unit = {
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val person = Person("")
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val result = new PatternMatching().extractors(person)
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assertEquals("Could not extract initials", result)
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}
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@Test
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def whenAListOfRandomElementsIsPassed_ThenOnlyTheIntegersBelowTenAreReturned(): Unit = {
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val input = List(1, 2, "5", 11, true)
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val result = new PatternMatching().closuresPatternMatching(input)
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assertEquals(List(1, 2), result)
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}
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@Test
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def whenAnExceptionIsPassed_ThenTheCorrespondingMessageIsReturned(): Unit = {
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val pm = new PatternMatching()
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val iae = new IllegalArgumentException()
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val re = new RuntimeException()
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val fnfe = new FileNotFoundException()
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assertEquals("It's an IllegalArgumentException", pm.catchBlocksPatternMatching(iae))
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assertEquals("It's a RuntimeException", pm.catchBlocksPatternMatching(re))
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assertEquals("It's an unknown kind of exception", pm.catchBlocksPatternMatching(fnfe))
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}
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}
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