Scala 中case模式匹配

最新推荐文章于 2024-04-19 16:09:11 发布

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最新推荐文章于 2024-04-19 16:09:11 发布 · 622 阅读

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#scala

本文介绍了Scala中的六种模式匹配技巧：简单匹配、类型匹配、守卫语句、for表达式、case类和Option类型，展示了如何在实际编程中灵活运用这些特性来处理不同数据类型和场景。

1. 简单匹配

object Test{
  def main(args: Array[String]): Unit = {
    val sex = -1
    val res = sex match {
      case 1 => "man"
      case 2 => "women"
//      case _ => "Not Allowed!" // other
      case unexcepted => unexcepted + " is Not Allowed!"
    }
    println(res)
  }
}
//-1 is Not Allowed!

或
val sex = -1
sex match {
  case 1 => println("man")
  case 2 => println("women")
  case _ => println(sex + " is Not Allowed!")
}

2. 类型匹配

object Test{
  def main(args: Array[String]): Unit = {
    for(e <- List(9, 12.3, "spark", "hadoop", 'Hello)){
      val res = e match {
        case _: Int => e + " is a int value."
        case _: Double => e + " is a double value."
        case "spark" => e
        case _: String => e + " is a string value."
        case _ => e + " is unknown."
      }
      println(res)
    }
  }
}
// 9 is a int value.
// 12.3