scala map的常用操作

 package cn.scala_base

 /**
  *  map常用操作
  */
 object Map {

   def main(args: Array[String]): Unit = {

     //1.不可变map(有序)
     val map1 = scala.collection.immutable.Map("wyc"->30,"tele"->20,"yeye"->100,"haha"->1000);
     println(map1("wyc"));
     println("map1---" + map1);

     //error
    // map1("wyc")=100;

     //2. 可变map
     val map2 = scala.collection.mutable.Map("wyc"->30,"tele"->20,"yeye"->100);
     map2("wyc")=10000;
     println(map2("wyc"));

     val map3 = scala.collection.mutable.Map(("wyc",100),("tele",1000),("yeye",10000));
     println(map3("wyc"));

     //3.创建HashMap(无序)
     val hashMap = new scala.collection.mutable.HashMap[String,Int];

     //为map增加元素
     hashMap += ("wyc"->1);
     println(hashMap("wyc"))

     //移除元素
     hashMap -= "wyc";

     //检查key是否存在
     if(hashMap.contains("wyc")) println(hashMap("wyc")) else println(0);

     //使用getOrElse进行检查
     println(hashMap.getOrElse("wyc","不存在"));

     //根据key进行排序的SortedMap,注意是immutable
     val sortedMap = scala.collection.immutable.SortedMap("wyc"->100,"tele"->1000);
     println("sortedMap----" + sortedMap);

     //有序的LinkedHashMap
     val linkedHashMap = scala.collection.mutable.LinkedHashMap("wyc"->100,"tele"->1000);
     println("linkedHashMap----" + linkedHashMap);

     //对于不可变的map1进行更新,其实是返回新的不可变map
     val mapX = map1 + ("newEntry"->1);
     val mapY = map1 - "wyc";

     //遍历Map
     for((key,value)<- map3) {
       println(key + ":" + value);
     }

     for(key <- map3.keySet) {
       println(key + ":" + map3(key));
     }

     //只遍历values
     /*for(value<-map3.values) {
       println(value);
     }*/

     //反转key与value
     val reverseMap = for((key,value)<-map3) yield (value,key);
     for(key<- reverseMap.keySet) {
       println(key + ":" + reverseMap(key));
     }

   }

 }