Scala模式匹配 match case
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2022-06-14 17:14:43
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1.匹配字符串/类型/守卫
val arr = Array("YoshizawaAkiho", "YuiHatano", "AoiSola")
val i = Random.nextInt(arr.length)
println(i)
val name = arr(i)
println(name)
name match {
case "YoshizawaAkiho" => println("吉泽老师...")
case "YuiHatano" => {
println("波多老师...")
}
case _ => println("真不知道你们在说什么...")
}
//定义一个数组
val arr:Array[Any] = Array("hello123", 1, 2.0, CaseDemo02, 2L)
//取出一个元素
val elem = arr(3)
elem match {
case x: Int => println("Int " + x)
case y: Double if(y >= 0) => println("Double "+ y) // if 守卫
case z: String => println("String " + z)
case w: Long => println("long " + w)
case CaseDemo02 => {
println("case demo 2")
}
case _ => {
// 其他任意情况
println("no")
println("default")
}
}2.匹配数组
示例：
val arr = Array(1, 1, 7, 0, 2,3)
arr match {
case Array(0, 2, x, y) => println(x + " " + y)
case Array(2, 1, 7, y) => println("only 0 " + y)
case Array(1, 1, 7, _*) => println("0 ...")
// _* 任意多个
case _ => println("something else")
}3.匹配集合
val lst = List(0, 3, 4)
println(lst.head)
println(lst.tail)
lst match {
case 0 :: Nil => println("only 0")
case x :: y :: Nil => println(s"x $x y $y")
case 0 :: a => println(s"value : $a")
case _ => println("something else")
}4.匹配元组
val tup = (1, 3, 7)
tup match {
case (3, x, y) => println(s"hello 123 $x , $y")
case (z, x, y) => println(s"$z, $x , $y")
case (_, w, 5) => println(w)
case _ => println("else")
}5.匹配样例/样例对象
//样例类，模式匹配，封装数据（多例）,不用 new 即可创建实例 case class SubmitTask(id: String, name: String)
case class HeartBeat(time: Long)
//样例对象，模式匹配（单例）
case object CheckTimeOutTask
val arr = Array(CheckTimeOutTask, new HeartBeat(123), HeartBeat(88888), new HeartBeat(666), SubmitTask("0001", "task-0001"))
val i = Random.nextInt(arr.length)
val element = arr(i)
println(element)
element match {
case SubmitTask(id, name) => {
println(s"$id, $name")
}
case HeartBeat(time) => {
println(time)
}
case CheckTimeOutTask => {
println("check")
}
}