一、集合的使用

1、不可变集合

  val listString= listOf<String>("one","two","one")println(listString)输出：[one, two, one]// set集合去重val setString= setOf<String>("one","two","one")println(setString)输出：[one, two]

2、可变集合

 val numbers= mutableListOf<Int>(1,2,3,4)numbers.add(6)numbers.removeAt(1)numbers[0]=10println(numbers)输出：[10, 3, 4, 6]//    set集合自动过滤重复元素val hello= mutableSetOf<String>("h","e","l","l","o")hello.remove("o")println(hello)输出:[h, e, l]//集合的加减操作：hello+=setOf("0","w","o","r","l","d")输出： [h, e, l, 0, w, o, r, d]

3、Map集合

   val numberMap= mapOf<String,Int>("a" to 1,"b" to 2,"c" to 3,"d" to 4)println("keys:${numberMap.keys}")println("values:${numberMap.values}")if ("a" in numberMap.keys){}if (2 in numberMap.values){}输出： 
keys:[a, b, c, d]
values:[1, 2, 3, 4]

二、集合的排序

1、随机排序

 val number2= mutableListOf<Int>(12,25,20,56,28)
//    随机排序number2.shuffled()println("随机$number2")输出：随机[12, 25, 20, 56, 28]

2、从小到大

//    从小到大排序number2.sort()println("小大${number2}")输出：小大[12, 20, 25, 28, 56]

3、从大到小

//    从大到小排序number2.sortedDescending()println("大小${number2.sortedDescending()}")输出:大小[56, 28, 25, 20, 12]

4、条件排序

  data class Language(var name:String,var score:Int)val languageList = mutableListOf<Language>()languageList.add(Language("java",88))languageList.add(Language("kotlin",98))languageList.add(Language("c语言",86))languageList.add(Language("python",80))languageList.add(Language("javascript",80))//    sortBy单条件排序languageList.sortBy { it.score }println(languageList)输出：[Language(name=python, score=80), Language(name=javascript, score=80), Language(name=c语言, score=86), Language(name=java, score=88), Language(name=kotlin, score=98)]//   sortWith 多条件排序languageList.sortWith(compareBy({it.score},{it.name}))println(languageList)输出：[Language(name=javascript, score=80), Language(name=python, score=80), Language(name=c语言, score=86), Language(name=java, score=88), Language(name=kotlin, score=98)]