获取从列表中

Question

第n个元素我有一个List

val family=List("1","2","11","12","21","22","31","33","41","44","51","55") 

我想利用它的第n个元素，但问题是，parents大小不固定。

val familliar=List("1","2","11") //n=3 

Answer 1

您可以使用take

scala> val list = List(1,2,3,4,5,6,7,8,9) 
list: List[Int] = List(1, 2, 3, 4, 5, 6, 7, 8, 9) 

scala> list.take(3) 
res0: List[Int] = List(1, 2, 3) 

Answer 2

使用take：

val familliar = family.take(3) 

Answer 3

List(1,2,3).take(100) //List(1,2,3) 

采取的签名会比较指数的说法，所以增量指标会比从不多论点

拍下的签名

override def take(n: Int): List[A] = { 
    val b = new ListBuffer[A] 
    var i = 0 
    var these = this 
    while (!these.isEmpty && i < n) { 
    i += 1 
    b += these.head 
    these = these.tail 
    } 
    if (these.isEmpty) this 
    else b.toList 
}