Android►Kotlin►集合►数组

Kotlin集合使用

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Kotlin动态

  • At the Google I/O keynote，Kotlin 成为 Android 官方编程语言

  • ACM-ICPC World Finals 2018将新增Kotlin作为编程语言

    集合

    集合类型Collections

    • 有序不可重复 -Array
    • 无序不重复 -set
    • 无序可重复 -Map

大小固定，元素类型不可变 

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fun main(array: Array<String>) {
var arrays = arrayOf("java","c","Kotlin")
   for (a in arrays ){
       println(a)
	    }
	}

创建默认值数组

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var arrays = Array(20, { "Kotlin" })

创建自增数组

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var count = Array(10, { i -> i + 1 })

数组常用方法

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//数组计数
 count.size
 //数组是否为空
 count.isEmpty()

过滤重复数组

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println(arrays.distinct())
//或
println(arrays.toSet())

提示：hashSetOf自身有去重

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   var has = hashSetOf("java", "Kotlin", "Kotlin", "Kotlin", "Kotlin", "Kotlin")
for (h in has) {
    println(h)
}
//输出结果  java Kotlin

切割数组

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val  Intercept=arrays.sliceArray(2..4)

大小可变，元素类型不可变

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var mutableListOfs = mutableListOf("java","c","C++","java","Visual Basic","	Scala","Kotlin","java","c","Kotlin")
    //数组末尾添加
    mutableListOfs.add("Swift")
    //添加一个数组
    mutableListOfs.addAll(arrays)

无序不重复

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val mainLine = setOf("Java", "Swift", "C++", "PHP", "Go", "Python")
val twoLine = setOf("C++", "C", "Ruby", "Objective-C")
val threeLine = setOf("C++", "Scala", "Dart")
//元素计数
println(mainLine.count())
//是否为空
println(mainLine.isEmpty())
//是否包含
println(mainLine.contains("Swift"))
println(mainLine.containsAll(twoLine))

转换数组

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val array = mainLine.toTypedArray()
for (a in array) {
    println(a)
}

集合运算

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val meetLines = mainLine.intersect(twoLine)//交集
println(meetLines)
val diffLine = mainLine.subtract(twoLine)//差集
println(diffLine)
println(mainLine.union(twoLine))//并集
println(mainLine.minus(twoLine))//补集

Map使用，没有顺序位置会改变

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val mapList = mapOf<String, String>(Pair("a", "1"), Pair("b", "1"), Pair("c", "1"), Pair("d", "1"))
   //获取key值
   println("a".toLowerCase())
   println("a".toUpperCase())
   println(mapList.getOrDefault("A".toLowerCase(), "不存在"))
   //返回所有key/value
   mapList.keys
   mapList.values

转换为可变

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val tmapList = mapList.toMutableMap()
   //修改
   tmapList["a"] = "8648"
   //添加
   tmapList.put("e", "156156")
   //移除
   tmapList.remove("a")
   for (t in tmapList) {
       println(t)
   }

Demo下载地址:https://github.com/Ysrfengnull/kt.git

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