Scala学习——模式匹配

scala模式匹配

1.基础match case(类似java里switch case,但功能强大些)

object MatchApp {

  def main(args: Array[String]): Unit = {
    val is = Array("a","b","c","d")
    val i = is(Random.nextInt(is.length))//随机取数组中的一个值
    i match {
      case "a" => println("aaa")
      case "b" => println("bbb")
      case "c" => println("ccc")
      case  _  => println("没有此匹配")
    }
  }

2、带条件的模式匹配

package top.ruandb.scala.Course05

import scala.util.Random

object MatchApp {

  def main(args: Array[String]): Unit = {
    judgeGrade("jack","A")//非常好
    judgeGrade("lucy","B")//好
    judgeGrade("lucy","D")//lucy同学，该努力学习了
    judgeGrade("jack","D")//同学，该努力学习了
  }

  def judgeGrade(name:String ,grade:String): Unit ={
    grade match{
      case "A" => println("非常好")
      case "B" => println("好")
      case "C" => println("一般")
      case _ if(name == "lucy")  => println(name+"同学，该努力学习了")//带条件筛选
      case  _ => println("同学，该努力学习了")
    }
  }
}

3、Array模式匹配

package top.ruandb.scala.Course05

import scala.util.Random

object MatchApp {

  def main(args: Array[String]): Unit = {

    greeting(Array("a"))//hi,a
    greeting(Array("b","c" ,"d"))//hi.everyone
    greeting(Array("a","b","c" ,"d"))//hi,a and others
    greeting(Array("c" ,"d"))//hi,c d

  }

  def greeting(array:Array[String]): Unit ={

    array match {
      case Array("a") => println("hi,a")//匹配数组Array("a")
      case Array(x,y) => println("hi,"+ x + " "+ y)//匹配两个元素的数组
      case Array("a",_*) => println("hi,a and others")//匹配以a开头的数组
      case _ => println("hi.everyone")
    }
  }

}

4、List模式匹配

package top.ruandb.scala.Course05

import scala.util.Random

object MatchApp {

  def main(args: Array[String]): Unit = {

    greeting(List("a"))//hi,a
    greeting(List("b","c" ,"d"))//hi.everyone
    greeting(List("a","b","c" ,"d"))//hi,a and others
    greeting(List("c" ,"d"))//hi,c d
  }

  def greeting(list:List[String]): Unit ={

    list match {
      case "a"::Nil => println("hi,a")//匹配只含a的List
      case x::y::Nil => println("hi,"+ x + " "+ y)//匹配两个元素的List
      case "a"::tail => println("hi,a and others")//匹配以a开头的List
      case _ => println("hi.everyone")
    }
  }

}

5、类型匹配

package top.ruandb.scala.Course05

import scala.util.Random

object MatchApp {

  def main(args: Array[String]): Unit = {

    matchType(1)//Int: 1
    matchType("str")//String; str
    matchType(Map("lucy"->18,"jack"->19,"kangkang"->99))//(lucy,18)(jack,19)(kangkang,99)
    matchType(3.14)//其他类型

  }
  def matchType(obj:Any): Unit ={
    obj match{
      case x:Int =>println("Int: "+ x )
      case s:String =>println("String; "+s)
      case m:Map[_,_] => m.foreach(println)
      case _ => println("其他类型")

    }
  }
}

6、异常处理

package top.ruandb.scala.Course05

object ExceptionApp {

  def main(args: Array[String]): Unit = {
    try{
      val i = 100/0 //ArithmeticException
      println(i)
    }catch {
      case e:ArithmeticException => println("分母不能为0")
      case e:Exception => println(e.getMessage)
    }finally {
      println("用于释放资源，一定能执行")
    }
  }
}

7、class模式匹配

package top.ruandb.scala.Course05

import scala.util.Random

object MatchApp {

  def main(args: Array[String]): Unit = {

    caseClassMatch(Cto("lucy","99"))
    caseClassMatch(Employee("jack","7"))
    caseClassMatch(Others("kangkang"))
  }

  def caseClassMatch(person:Person): Unit ={
    person match{
      case Cto(name,floor) => println("hi,"+name +" "+ floor)
      case Employee(name,floor) =>println("hi,"+name +" "+ floor)
      case Others(name) => println("hi,"+name )
    }
  }

  class Person
  case class Cto(name:String,floor:String) extends  Person
  case class Employee(name:String,floor:String) extends Person
  case class Others(name:String) extends  Person
}

8、Some,None模式匹配

package top.ruandb.scala.Course05

import scala.util.Random

object MatchApp {

  def main(args: Array[String]): Unit = {

    getGrade("lucy")//your grade is A
    getGrade("jack")//your grade is B
    getGrade("kangkang")//without your score

  }

  val grades = Map("lucy"->"A","jack"->"B")
  def getGrade(name:String): Unit ={
    val grade = grades.get(name)
    grade match{
      case Some(grade) => println("your grade is "+ grade)
      case None =>println("without your score")
    }
  }
}