Kotlin笔记6-Lambda编程1-集合的创建与遍历-List,Set,Map

4.1 Lambda编程1

• 集合

Java接口

1. List

List

集合逐个添加

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

listOf: 不可变集合

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

mutableListOf: 可变集合

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

2. Set

Set

Set初始化

SetOf: 不可变集合

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

mutableSetOf: 可变集合

3. Map

Map: 键值对形式数据结构

Map添加数据(不推荐)

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)//不推荐

Map添加数据(推荐)

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

读取数据

val number=map1["Apple"]

Map添加数据(简化)

to: infix函数

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

​​Example:​​

fun main() {
    //再简化
    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.")
    }
}