scala利用map，从命令行读一个字符串，表示一个年份，输出该年的世界杯冠军

以下是一个Scala程序示例，可以从命令行读取一个字符串作为年份，然后利用Map结构输出该年的世界杯冠军：

object WorldCupChampions {
  def main(args: Array[String]): Unit = {
    val champions = Map(
      1930 -> "Uruguay",
      1934 -> "Italy",
      1938 -> "Italy",
      1950 -> "Uruguay",
      1954 -> "West Germany",
      1958 -> "Brazil",
      1962 -> "Brazil",
      1966 -> "England",
      1970 -> "Brazil",
      1974 -> "West Germany",
      1978 -> "Argentina",
      1982 -> "Italy",
      1986 -> "Argentina",
      1990 -> "West Germany",
      1994 -> "Brazil",
      1998 -> "France",
      2002 -> "Brazil",
      2006 -> "Italy",
      2010 -> "Spain",
      2014 -> "Germany",
      2018 -> "France"
    )

    if (args.length == 0) {
      println("Please enter a year.")
    } else {
      val year = args(0).toInt
      champions.get(year) match {
        case Some(champion) => println(s"The champion of $year is $champion.")
        case None => println("No World Cup was held in that year.")
      }
    }
  }
}

该程序首先定义了一个Map结构，其中键是世界杯的年份，值是该年的冠军国家。然后，程序从命令行读取一个字符串作为年份，将其转换为整数后在Map中查找对应的冠军。如果找到了，程序输出该年的冠军国家；否则，输出“在该年没有世界杯举办”的消息。