kotlin普通列表

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val list = listOf("jack", "lucy", "black")
println(list.getOrElse(4) { "UnKnown" })
println(list.getOrNull(4) ?: "UnKnown")
println(list[2])

list的for each循环

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val list = listOf("jack", "jimmy", "jason")

for (s in list) {
    println(s)
}

list.forEach {
    println(it)
}

list.forEachIndexed { index, s ->
    println("$index  $s")
}

//此处的_参数被过滤掉，name proxy依次赋值0 1个元素
val (name,_,proxy) = listOf("jack","jimmy","jason","jacky")
println("name = $name   proxy = $proxy")

map列表

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//此处用了infix函数
val map = mapOf("jack" to 20, "jimmy" to 18, "jason" to 24)
println(map)

//pair是map的子元素
val sMap = mapOf(Pair("jack", 20), Pair("jimmy", 18), Pair("json", 24))
println(map["jack"])
println(sMap["jimmy"])

//
println(map.getOrElse("jimmy") { "UnKnown" })
println(map.getOrDefault("jason") { "UnKnown" })

//map的遍历
map.forEach {
    println("${it.key}  ${it.value}")
}

//map的遍历
map.forEach { (key, value) ->
    println("key = $key  value = $value")
}

kotlin可变列表MutableList

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val mutableList = mutableListOf("jack", "jimmy", "jacky")
mutableList.add("jason")
mutableList.remove("jack")
println(mutableList)

listOf("a", "b", "c").toMutableList()
mutableListOf("m", "n", "o").toList()

kotlin可变列表MutableMap

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val mutableMap = mutableMapOf("Jack" to 20, "Jason" to 18, "Jacky" to 30)
//此处用到了操作符重载
mutableMap += "jimmy" to 1000
mutableMap.put("lucas", 31)
mutableMap["lucy"] = 30

mutableMap.getOrPut("lily"){ 100 }
val i = mutableMap.getOrPut("jimmy"){ 100 }

println(mutableMap)
println(i)

set列表

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val mutableSet = mutableSetOf("Kotlin", "Java", "Scala")
mutableSet += "Groovy"

println(listOf("Jack", "Jason", "Jacky","Jacky").toSet().toList())

//去重的快捷函数
println(listOf("Jack", "Jason", "Jacky","Jacky").distinct())
赏

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