Spark學習使用筆記 - Scala篇（3）- 映射，元組

映射：

def constructMap = {
    //構造一個不可變Map[String Int]
    val scores = Map("Alice" -> 10, "aaa" -> 9, "bbb" -> 5)
    //構造一個可變Map[String,Int]
    val mscores1 = scala.collection.mutable.Map("Alice" -> 10, "aaa" -> 9, "bbb" -> 5)

    val mscores2 = scala.collection.mutable.Map(("Alice", 10), ("aaa", 9), ("bbb", 8))
  }

  def curdMap = {
    val scores = scala.collection.mutable.Map("Alice" -> 10, "aaa" -> 9, "bbb" -> 5)
    println(scores.mkString("<", ",", ">"))//輸出：<bbb -> 5,aaa -> 9,Alice -> 10>
    //val bobScore = scores("Bob") //找不到拋異常
    val aliceScore = scores("Alice")
    val bobScore = scores.getOrElse("Bob", 6)
    println(aliceScore)//輸出：10
    println(bobScore)//輸出：6

    scores("Alice") = 9
    println(scores("Alice"))//輸出：9

    scores += ("Bob" -> 7)
    println(scores.mkString("<", ",", ">"))//輸出：<bbb -> 5,Bob -> 7,aaa -> 9,Alice -> 9>

    scores -= "Bob"
    println(scores.mkString("<", ",", ">"))//輸出：<bbb -> 5,aaa -> 9,Alice -> 9>
  }

  def traverseMap = {
    val mapping = Map("Alice" -> 10, "aaa" -> 9, "bbb" -> 5)
    val a = for ((k, v) <- mapping) yield k + ":" + v
    println(a)//輸出：List(Alice:10, aaa:9, bbb:5)
    val b = for (k <- mapping.keys) yield k
    println(b)//輸出：Set(Alice, aaa, bbb)
    val c = for (v <- mapping.values) yield v
    println(c)//輸出：List(10, 9, 5)
  }

  def sortedMap = {
    //scala自己只有不可變排序Map（樹形Map）
    val mapping = SortedMap("Alice" -> 10, "aaa" -> 9, "bbb" -> 5)
    println(mapping.mkString("<", ",", ">"))//輸出：<Alice -> 10,aaa -> 9,bbb -> 5>
  }

元組：

def test = {
    val tuple1 = (1, 2, 3, 9.0, "hello")
    val element1 = tuple1._1
    println(element1)//輸出：1

    val (_, second, third, _, _) = tuple1
    println(second)//輸出：2
    println(third)//輸出：3

  }

鏈式操做：

def test = {
    val key = Array("zhx", "dick", "hash")
    val value = Array(1, 2, 3)
    val keyvalue = key.zip(value)
    val map = keyvalue.toMap

    println(map.mkString("<", ",", ">"))//輸出：<zhx -> 1,dick -> 2,hash -> 3>
  }