Scala模式匹配和样例类

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

??????val charStr = ‘6‘

??????charStr match {

????????case ‘+‘ => println("匹配上了加号")

????????case ‘-‘ => println("匹配上了减号")

????????case ‘*‘ => println("匹配上了乘号")

????????case ‘/‘ => println("匹配上了除号")

??????????//注意。所有的模式匹配都必须最终匹配上一个值，如果没有匹配上任何值，就会报错

?????? // case _??=> println("都没有匹配上，我是默认值")

??????}

????}

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

??????val arr = Array("hadoop","zookeeper","spark")

??????val name = arr(Random.nextInt(arr.length))

??????name match {

????????case "hadoop"????=> println("大数据分布式存储和计算框架...")

????????case "zookeeper" => println("大数据分布式协调服务框架...")

????????case "spark" => println("大数据分布式内存计算框架...")

????????case _ => println("我不认识你...")

??????}

? ?

}

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

???????? var ch = "500"

???????? var sign = 0

???????? ch match {

???????? case "+" => sign = 1

???????? case "-" => sign = 2

???????? case _ if ch.equals("500") => sign = 3

???????? case _ => sign = 4

???????? }

???????? println(ch + " " + sign)

????????}

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

//注意泛型擦除，在模式匹配当中的类型匹配中，除了Array类型以为，所有的其他的数据类型都会被擦除掉

val a = 3

val obj = if(a == 1) 1

else if(a == 2) "2"

else if(a == 3) BigInt(3)

else if(a == 4) Map("aa" -> 1)

else if(a == 5) Map(1 -> "aa")

else if(a == 6) Array(1,2,3)

else if(a == 7) Array("aa",1)

else if(a == 8) Array("aa")

val r1 = obj match {

case x: Int => x

case s: String => s.toInt

case BigInt => -1 //不能这么匹配

case _: BigInt => Int.MaxValue

case m: Map[String,Int] => "Map[String,Int]类型的Map集合"

case m: Map[_,_] => "Map集合"

case a: Array[Int] => "It‘s an Array[Int]"

case a: Array[String] => "It‘s an Array[String]"

case a: Array[_] => "It‘s an array of something other than Int"

case _ => 0

}

println(r1 + "," + r1.getClass.getName)

}

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

val arr = Array(0,3,5)

arr match {

case Array(0,x,y) => println(x + " " + y)

case Array(0) => println("only 0")

//匹配数组以1 开始作为第一个元素

case Array(1,_*) => println("0 ...")

case _ => println("something else")

}

? ?

val lst = List(3,-1)

lst match {

case 0 :: Nil => println("only 0")

case x :: y :: Nil => println(s"x: $x y: $y")

case 0 :: tail => println("0 ...")

case _ => println("something else")

}

? ?

val tup = (1,7)

tup match {

case (1,y) => println(s"1,$x,$y")

case (_,z,5) => println(z)

case _ => println("else")

}

}

case class SubmitTask(id: String,name: String)

case class HeartBeat(time: Long)

case object CheckTimeOutTask

//1、样例类当中的主构造器参数默认为val的

//2、样例类当中的apply和unapply方法自动生成

object CaseDemo04 extends App {

val arr = Array(CheckTimeOutTask,HeartBeat(12333),SubmitTask("0001","task-0001"))

arr(2) match {

case SubmitTask(id,name) => {

println(s"$id,$name")

println(id)

println(name)

println(id+"t"+name)

}

case HeartBeat(time) => {

println(time)

}

case CheckTimeOutTask => {

println("check")

}

}

}

????????????????val func1: PartialFunction[String,Int] = {

???????????????? case "one" => 1

???????????????? case "two" => 2

???????????????? // case _ => -1

????????????????}

???????????????? ?

????????????????def func2(num: String) : Int = num match {

???????????????? case "one" => 1

???????????????? case "two" => 2

???????????????? case _ => -1

????????????????}

???????????????? ?

????????????????def main(args: Array[String]) {

???????????????? println(func1("one"))

???????????????? println(func2("one"))

???????????????? //如果偏函数当中没有匹配上，那么就会报错，我们可以通过isDefinedAt来进行判断

???????????????? // println(func1("three"))

???????????????? println(func1.isDefinedAt("three"))

???????????????? if(func1.isDefinedAt("three")){

???????????????? println("hello world")

???????????????? }else{

???????????????? println("world hello")

???????????????? }

????????????????}