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1、Scala中List、Map、Set等各類型函數(shù)操作匯總
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)) //單個(gè)元素聯(lián)合List:List(1, 2, 3, 4)
//兩個(gè)List進(jìn)行聯(lián)合成一個(gè)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)
//將List集合拆分成2個(gè)List集合:(List(1,2,3),List(4,5,6))
println(List(1, 2, 3, 4, 5, 6).span(_ < 4))
//將List集合中的元素用“—”進(jìn)行拼接
println(List("a", "b", "c", "d").mkString("_"))
//將List集合元素進(jìn)行拆分,合并成一個(gè)大的List集合
println(List("Spark", "Hadoop").flatMap(_.toList))
//exists判斷List集合中是否存在元素,forall是判斷整行情況
println(List(List(1, 0, 0), List(0, 1, 0), List(0, 0, 0)).exists(row => row.forall(_ == 0)))
/**
* foldLeft就是每次計(jì)算的結(jié)果加上List集合中的元素
* 如:1+0=1,2+1=3,3+3=6,4+6=10,5+10=15,...=5050
*/
println((1 to 100).toList.foldLeft(0)(_ + _))
/**
* foldRight就是每次List集合中的元素減去計(jì)算結(jié)果
* 如:1-100 = -99,2-(-99) = 101,3-101 = -98,4-(-98) = 102,5-102 = -97
*/
println(List(1, 2, 3, 4, 5).foldRight(100)(_ - _))
println(List.apply(1, 2, 3, 4, 5))
println(List("b", "e", "a", "f").sortWith(_ < _)) //List排序輸出
println(List.make(3, 5)) //構(gòu)造List重復(fù)元素:List(5,5,5)
println(List.range(1, 5)) //List(1,2,3,4)
println(List.range(1, 9, 3)) //List中的元素是按間隔生成:List(1,4,7)
//拉鏈操作: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) //解拉鏈:(List(a, b, c, d, e),List(1, 2, 3, 4, 5))
//List集合進(jìn)行合并:List(1, 2, 3, 4, 5)
println(List(List(1, 2), List(3, 4), List(5)).flatten)
//List集合進(jìn)行合并:List(1, 2, 3, 4, 5)
println(List.concat(List(1, 2), List(3, 4), List(5)))
//兩個(gè)List按給定的函數(shù)進(jìn)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)
//創(chuàng)建可變Set
val data = mutable.Set.empty[Int]
data ++= List(2, 3, 4)
data += 4 //Set:重復(fù)數(shù)據(jù)不會(huì)添加
println(data)
data --= List(2, 3) //移除List集合
println(data)
data.clear() //清空Set集合
println(data)
//創(chuàng)建可變Map
val map = mutable.Map.empty[String, String]
map("Java") = "Hadoop"
map += {
"Scala" -> "Spark"
}
map += ("Scala" -> "Tachyon") //相同Key,value值覆蓋
println(map)
println(map("Java"))
for ((k, v) <- map) println(k + ":" + v)
//創(chuàng)建treeSet,輸出是按升序排序的
val treeSet = mutable.TreeSet(9, 2, 3, 8, 6, 7, 5, 1)
treeSet += 4
println(treeSet)
val treeSetForStr = mutable.TreeSet("Spark", "Hadoop", "Kafka", "Tachyon")
println(treeSetForStr)
//創(chuàng)建treeMap
val treemap = TreeMap("Scala" -> "Spark", "Java" -> "Hadoop")
println(treemap)
}
}
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