scala 循环

object test1 {
  def main(args: Array[String]): Unit = {

    val s1 = List("DDD","99990","Shall")
    println("8"*88+"第一种")
    for (elem <- s1) {println(elem)}
    println("8"*88+"第二种")
    for (elem <- s1) {
      if(elem.length>3)
        println(elem)
    }
    println("8"*88+"第三种")

    var s2 =
    for {elem <- s1
      if(elem.length>3)
        st = elem.toUpperCase()
    }yield(st)
    for (elem <- s2) {println(elem)}

    println("8"*88+"第四种")
    var i = 0
    while(i<s2.length){
      println(s2(i))
      i+=2
    }
    for (x <- 1 until 20)println(x)
  }
}