Scala--映射和元组

  val scores = Map("Jim"->10, ("Tom",20), "Sam"->44) //key->value, (key,value)两种方式表示, 不可变映射，
  val s = scala.collection.mutable.Map("Jim"->10, ("Tom",20), "Sam"->44)//可变映射
  val s1 = new scala.collection.mutable.HashMap[String, Int] //空的Map

  //scores.+=(("Lily"->10))  //不可变映射，map中不能新增元素
  s.+=(("Lily"->10))
  s1.+=(("Jim"->10))

  println(scores)
  println(s)
  println(s1)

Map(Jim -> 10, Tom -> 20, Sam -> 44)
Map(Jim -> 10, Tom -> 20, Lily -> 10, Sam -> 44)
Map(Jim -> 10)

  val scores = Map("Jim"->10, ("Tom",20), "Sam"->44)

  val score1 = scores("Lily")  //直接通过()获取里面的值
  val score2 = if(scores.contains("Lily")) scores("Lily") else 0 //判断是否存在，然后再取值
  val score3 = scores.getOrElse("Lily",0) //通过getOrElse方法实现，不存在给默认值

  println(score1)
  println(score2)
  println(score3)

  val scores = scala.collection.mutable.Map("Jim"->10, ("Tom",20), "Sam"->44)

  scores("Jim") = 11      //更新值
  scores("Fred") = 33     //新增值

  scores += ("Lily"->30, "Li"-> 27) //增加多个
  scores.+=(("Zhao"->44))
  scores -= "Jim"      //删除元素

  println(scores)

Map(Li -> 27, Zhao -> 44, Fred -> 33, Tom -> 20, Lily -> 30, Sam -> 44)

  var scores = Map("Jim"->10, ("Tom",20), "Sam"->44)

  scores = scores +("Lily"-> 23)
  scores -= "Jim"

  println(scores)

Map(Tom -> 20, Sam -> 44, Lily -> 23)

  var scores = Map("Jim"->10, ("Tom",20), "Sam"->44)

  for((k, v) <- scores) println (k+","+v)
  for(i<- scores.keySet) print(i+" ")
  println()
  for(i<- scores.values) print(i+" ")

Jim,10
Tom,20
Sam,44
Jim Tom Sam 
10 20 44 

  val sortedScores = scala.collection.immutable.SortedMap("Jim"->10, ("Tom",20), "Sam"->44)
  println(sortedScores)

Map(Jim -> 10, Sam -> 44, Tom -> 20)

  val tuple = (1, 3.14, "Hello")
  println(tuple._1)  //访问第一个元组，下标值不是0而是1
  val(first, second, _) = tuple //获取元组的元素
  println(second)

1
3.14

  val symbols = Array("<","-",">")
  val counts = Array(2,10,2)
  val pairs = symbols.zip(counts)

  for((k,v)<- pairs) print(k * v)

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