今天要介绍的是list set 和 map。
List 是只可读 , 不可修改
var list :List<String> = listOf("i","r","o","m", "m","a","n")
//list[3] = "n" IDE 不允许修改
println("list[3] = "+list[3])
取不到回传空白
println("getOrElse 取不到回传空白 = "+list.getOrElse(7) {""})
取不到回传 null
println("getOrNull 取不到回传null = "+list.getOrNull(7)) //null
Contains 判断元素,是否包含在 List 集合内
println(list.contains("i")) //true
println(list.containsAll(listOf("i", "m"))) //true
MutableList 是可读写,可以修改
var mList:MutableList<String> = mutableListOf("i","t","h","o","n","e")
println("before mList[4] = "+mList[4])
mList[4] = "m" //hone 要改 home
println("Change mList[4] = "+mList[4])
新增add
mList.add("d")
println("add d = "+mList)
删除remove
mList.remove("d")
println("remove d = "+mList)
再删一次一样值 remove again
mList.remove("d")
println("remove d = "+mList)
用index来删除 remove by index
mList.removeAt(0)
println("removeAt by Index = "+mList)
List ForEach
list.forEach { println("ForEach list = "+it) }
List ForEachIndex
list.forEachIndexed { index, value ->
println("$index, $value")
}
Set 和list不同的地方,就是set里面的内容不可重覆
val set = setOf("i","r","o","m", "m","a","n")
println(" Set = "+set) // i r o m a n
val mSet = mutableSetOf("i","r","o","m", "m","a","n")
println(" mSet = "+set) // i r o m a n
contains判断元素,是否包含在 Set 集合内
println(set.contains("i")) //true
println(set.elementAt(0)) //A
Map 用 "to" 给值
var kotlin_team = mapOf("total_day" to 30, "start_day" to 96, "end_day" to 105)
println("kotlin_team = "+kotlin_team)
Map 新增 add key value
kotlin_team += "after_day" to 7
println("add key value kotlin_itaiwan = "+kotlin_team)
Map 用 "Pair" 给值
var kotlin_itaiwan = mapOf(Pair("total_day" , 30), Pair("start_day" ,96) ,
Pair("end_day", 105))
println("kotlin_itaiwan = "+kotlin_itaiwan)
Map 新增add key value
kotlin_itaiwan += "after_day" to 7
println("add key value kotlin_itaiwan = "+kotlin_itaiwan)
Map 取值 , 变数["key"]
println("kotlin_team[total_day] = "+kotlin_team["total_day"])
执行结果:
https://kotlinlang.org/docs/list-operations.html
https://kotlinlang.org/docs/set-operations.html
https://kotlinlang.org/docs/map-operations.html
<<: [C 语言笔记--Day01] Hello World
那今天我们来聊聊,怎麽透过cypress来验证url的路径吧,重回昨天的范例,我们想要透过一个按钮,...
所谓的主力,就是有绝对多的资金,或是大量持有某一档股票,最大的优势就是容易操控股票价格。 今年一堆散...
昨天,我们已建立完决策树,那今天,我打算带入资料去看他分类结果: 建立决策树的使用模型: #用树来预...
终於到了最後一篇了,就来讲讲这次发铁人赛文的感想吧! 过程分享 这次铁人赛其实有先囤了一些文章,可是...
在对照着看翻译结果和原文时,需要不断卷动画面。如果两边画面可以同步卷动的话,就能省下手指在两个 We...