【Kotlin】Kotlin筆記6-Lambda程式設計1(List,Set,Map)

Kotlin筆記6-Lambda程式設計1-集合的建立與周遊-List,Set,Map

4.1 Lambda程式設計1

• 集合

Java接口

List	Set	Map
ArrayList,LinkedList	HashSet	HashMap

1. List

List

集合逐個添加

val list = ArrayList<String>()
list.add("Apple")
list.add("Banana")
...      

listOf: 不可變集合

val list = listOf("Apple", "Banana", "Orange", "Pear", "Grape")      

mutableListOf: 可變集合

val list1= mutableListOf("Apple", "Banana", "Orange", "Pear", "Grape")
list1.add("watermelon")      

1. Set

Set

Set初始化

SetOf: 不可變集合

val set= setOf("Apple","Banana","Orange","Pear","Grape")      

mutableSetOf: 可變集合

1. Map

Map: 鍵值對形式資料結構

Map添加資料(不推薦)

val map=HashMap<String,Int>()
    map.put("Apple",1)
    map.put("Banana",2)
    map.put("Orange",3)
    map.put("Pear",4)
    map.put("Grape",5)//不推薦      

Map添加資料(推薦)

val map1=HashMap<String,Int>()
    map1["Apple"] = 1
    map1["Banana"] = 2
    map1["Orange"] = 3
    map1["Pear"] = 4
    map1["Grape"] = 5//推薦      

讀取資料

val number=map1["Apple"]      

Map添加資料(簡化)

to: infix函數

val map2= mapOf("Apple" to 1,"Banana" to 2,"Orange" to 3,"Pear" to 4,"Grape" to 5)      

fun main() {
    //再簡化
    val map= mapOf("Apple" to 1,"Banana" to 2,"Orange" to 3,"Pear" to 4,"Grape" to 5)
    for((fruit,number) in map){
        println("fruit is $fruit ,number is $number.")
    }
}