list 集合笔记

1.创建和获取

var list = listOf<String>("ss", "ss")
list[3]//越界
list.getOrElse(3) { "Unknown" }//Unknown
list.getOrNull(3)//null
list.getOrNull(3) ?: "Unknown"//Unknown

2.可变列表

val mutableList = mutableListOf<String>("ss","bb")
mutableList.add("zz")
mutableList.remove("ss")

3.运算符+= 同 add() ,-=同 remove()
4.removeIf

val mutableList = mutableListOf<String>("ss","bb")
mutableList.removeIf{
    it=="ss"
}
println(mutableList)
输出：
[bb]

5.forEach 遍历

val mutableList = mutableListOf<String>("ss","bb")
mutableList.forEach{
    println(it)
}
输出：
ss
bb

6.forEachIndexed 遍历

val mutableList = mutableListOf<String>("ss","bb")
mutableList.forEachIndexed{index,item->
    println("$index $item")
}
输出：
0 ss
1 bb

7.解构

 val mutableList = mutableListOf<String>("ss","bb")
val (ss) = mutableList
prrintln(mutableList[0])
 println(ss)
 输出：
 ss
 ss