Kotlin 基础教程之数组容器

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Kotlin 基础教程之数组容器

Arrays

Kotlin 标准库提供了arrayOf()创建数组， **ArrayOf创建特定类型数组

val array = arrayOf(1, 2, 3) val countries = arrayOf("UK", "Germany", "Italy") val numbers = intArrayOf(10, 20, 30) val array1 = Array(10, { k -> k * k }) val longArray = emptyArray() val studentArray = Array(2) studentArray[0] = Student("james")

和Java不一样，Kotlin 的数组是容器类， 提供了 ByteArray, Chararray, ShortArray, IntArray, LongArray, BooleanArray, FloatArray, and DoubleArray。

Lists

List是有序容器，Kotlin 标准库通过listof()创建list

val intList: List = listof(20, 5, 10) val emptyList: List = emptyList() val nonNulls: List = listofNotNull(null, "a", "b", "c") val doubleList: ArrayList = arraylistof(84.88, 100.25, 999.99)

其中，intList, emptyList, nonNulls是只读的实例，要修改这些list，需要进行类型转换

(intList as AbstractList).set(0, 30) (nonNulls as java.util.ArrayList).addAll(arrayOf("x", "y"))

Maps

Map是容器， Kotlin提供mapOf创建map

val map = mapOf("a" to 1, "b" to 2, "c" to 3) val value = map.get(b) val states: MutableMap= mutableMapOf("AL" to "Alabama", "AK" to "Alaska", "AZ" to "Arizona") val customers: java.util.HashMap = hashMapOf(1 to Customer("Dina", "Kreps", 1), 2 to Customer("Andy", "Smith", 2)) val linkedHashMap: java.util.LinkedHashMap = linkedMapOf("red" to "#FF0000","azure" to "#F0FFFF","white" to "#FFFFFF") val sortedMap: java.util.sortedMap = sortedMapOf(4 to "d", 1 to "a", 3 to "c", 2 to "b")

Sets

Set是没有重复项的容器， Kotlin提供setof创建Set

val intSet: Set = setof(1, 21, 21, 2, 6, 3, 2) //1,21,2,6,3 val hashSet: java.util.HashSet = hashSetof( Book("Jules Verne", "Around the World in 80 Days Paperback", 2014, "978-1503215153"), Book("Jules Verne", "Around the World in 80 Days Paperback", 2014, "978-1503215153")) val sortedIntegers: java.util.TreeSet = sortedSetof(11, 0, 9, 11, 9, 8)

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