kotlin 集合

 

一、List

1.

    var list1 = listOf(1, 3, 5)
    //
    println(list1.map { it * 10 })//[10, 30, 50]
    //筛选list
    println(list1.filter { it>3 }) //[5]
    //筛选list 后的个数
    print(list1.count{it>3}) //1
　　//求和
    print(list1.sum())//9

2.对象里的某个属性求和 

data class Student(val name:String,val score:Int)

fun main() {
    val student1 = Student("tom", 100)
    val student2 = Student("liu", 100)
    val student3 = Student("li", 150)
    var list= listOf(student1,student2,student3)
    print(list.sumBy { it.score })   //350
}

3.递归

    var list1 = listOf(1, 3, 5)
    //递归调用fold(n)里的n是初始值
    print(list1.fold(2) { n, s -> n * s })

 

 

二、Set

 

三、Map