Summary of List, Map and Set operations in Scala

1. Operation summary of List, Map, Set and other functions in Scala

Package com.scala.study

Import scala.collection.immutable. {Queue, TreeMap}

Import scala.collection.mutable

/ * *

* Created by HP-PC on 2016-5-26.

, /

Object ScalaCaseDemo {

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

Println (1:: 2:: List (3,4)) / / single element joint List:List (1,2,3,4)

/ / two List are combined to form a List:List (1, 2, 3, 4)

Println (List (1,2): List (3,4))

Println (List ("Spark", "Hadoop", "Hive") .head) / / Spark

Println (List ("Spark", "Hadoop", "Hive"). Tail) / List (Hadoop, Hive)

/ / split the List set into 2 List sets: (List (1meme 2p3), List (4meme 5pc6))

Println (List (1,2,3,4,5,6). Span (_

< 4)) //将List集合中的元素用"-"进行拼接 println(List("a", "b", "c", "d").mkString("_")) //将List集合元素进行拆分，合并成一个大的List集合 println(List("Spark", "Hadoop").flatMap(_.toList)) //exists判断List集合中是否存在元素，forall是判断整行情况 println(List(List(1, 0, 0), List(0, 1, 0), List(0, 0, 0)).exists(row =>

Row.forall (_ = = 0))

/ * *

* foldLeft is the result of each calculation plus the elements in the List collection

* for example: 1, 1, 1, 1, 1, 3, 3, 3, 6, 6, 6, 10, 10, 10, 15, 15, 5, 10, 15, 5, 10, 15, 5050.

, /

Println ((1 to 100) .toList.foldLeft (0) (_ + _)

/ * *

* foldRight is the element in each List collection minus the calculation result.

* for example: 1-100 =-99 ~ (- 99) = 101 ~ (101) =-98 ~ (- 98) = 102 ~ (- 97)

, /

Println (List (1,2,3,4,5) .foldRight (100,100) (_ _))

Println (List.apply (1,2,3,4,5))

Println (List ("b", "e", "a", "f") .sortWith (_

< _)) //List排序输出 println(List.make(3, 5)) //构造List重复元素：List(5,5,5) println(List.range(1, 5)) //List(1,2,3,4) println(List.range(1, 9, 3)) //List中的元素是按间隔生成：List(1,4,7) //拉链操作：List((a,1), (b,2), (c,3), (d,4), (e,5)) val zipped = "abcde".toList zip List(1, 2, 3, 4, 5) println(zipped) println(zipped.unzip) //解拉链：(List(a, b, c, d, e),List(1, 2, 3, 4, 5)) //List集合进行合并：List(1, 2, 3, 4, 5) println(List(List(1, 2), List(3, 4), List(5)).flatten) //List集合进行合并：List(1, 2, 3, 4, 5) println(List.concat(List(1, 2), List(3, 4), List(5))) //两个List按给定的函数进行操作：List(300, 1200) println(List.map2(List(100, 200), (List(3, 6)))(_ * _)) val empty = Queue[Int]() val queue1 = empty.enqueue(1) val queue2 = queue1.enqueue(List(2, 3, 4, 5)) println(queue2) val (element, left) = queue2.dequeue println(element + ":" + left) //创建可变Set val data = mutable.Set.empty[Int] data ++= List(2, 3, 4) data += 4 //Set:重复数据不会添加 println(data) data --= List(2, 3) //移除List集合 println(data) data.clear() //清空Set集合 println(data) //创建可变Map val map = mutable.Map.empty[String, String] map("Java") = "Hadoop" map += { "Scala" ->

"Spark"

}

Map + = ("Scala"-> "Tachyon") / / same Key, overridden by value

Println (map)

Println (map ("Java"))

For ((k, v) "Spark", "Java"-> "Hadoop")

Println (treemap)

}

}