Scala集合类（四）

本文链接： https://blog.csdn.net/weixin_42568742/article/details/89387462

import scala.collection.mutable 可变集合包
import scala.collection.immutable 不可变集合包，默认不可变

1、可变list

val list2 = ListBuffer[Int](1,2,3)
    list2.append(4,5,6)
    list2.foreach(println)

2、不可变list

   val list = List[String]("hello scala","hello java","hello spark")
    val list1 = list.flatMap(s=>{s.split(" ")})//flatMap一对多
   // list1.foreach(println(_))

//    val result  = list.map(a=>a.split(" "))//map一对一关系
//    result.foreach(arr=>{
//      println("新的数组：")
//      arr.foreach(println)})

    //val list = List(1,2,3,4,"true")
//    val list = List[Int](1,2,3)
    //list.foreach(println(_))
//    for(elem<-list){
//      println(elem)
//    }

3、可变长set集合—— mutable.Set

val set5 = mutable.Set[Int](1,2,3)
      set5.+=(100)
    set5.foreach(println(_))

4、set集合无序，并且不重复，默认不可变长
immutable.Set

 val set = immutable.Set[Int](1,2,4,4,5)
    val set1 = Set[Int](3,4,5,6)
    val set2 = set.intersect(set1)//取交集set & set1 操作符操作
    val set3 = set.diff(set1)//取差集set &` set1
   // set3.foreach(println(_))

5、可变长度map mutable.MapString,Int

l map4 = mutable.Map[String,Int]()
    map4.put("a",100)
    map4.put("b",200)
    map4.foreach(println(_))

6、不可变map

val map1 = Map[String,Int](("a",1),("b",2),("c",3),("d",4))
      val map2 = Map[String,Int](("a",100),("b",2),("c",300),("e",4))
    val stringToInt = map1.++(map2)
    val stringToInt2 = map1.++:(map2)
    //stringToInt2.foreach(println(_))



    val map = Map[String,Int]("a"->100,"b"->200,("c",300),("c",400))

    val keys = map.keys
    keys.foreach(key=> {
      val value = map.get(key).get
 //     println(s"key = $key,value = $value")
    }
    )


    val value = map.get("aa").getOrElse("No value")
   // println(value)
    //println(map)//Map(a -> 100, b -> 200, c -> 400)
//    for(elem<-map){
//      println(elem)
//    }
   // map.foreach(println(_))

7、元组

/**
      * 元组最多支持22个元素
      * 元组可new，可不new，可直接写()中元素
      */
    val tuple1 = new Tuple1("hello")
    val tuple2 = new Tuple2("a",100)
    val tuple3 = new Tuple3(1,true,'c')
    val tuple4 = Tuple4(1,3.4,"abc",true)
    val tuple22 = Tuple22(1,2,3,4,5,6,7,8,9,10,11,12,"abc",14,15,16,17,18,19,20,21,22)
    //println(tuple22._13)
    /**
      * 遍历
      */

    val iterator = tuple22.productIterator
    iterator.foreach(println(_))
//    while (iterator.hasNext){
//      println(iterator.next())

Scala集合类（四）

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