scala语言入门（三）scala集合
【摘要】 一、定长数组和变长数组
package com.dzx.listPack import scala.collection.mutable.ArrayBuffer object ArrayApp extends App { //1.定长数组 val a = new Array[String](5) a.length a(0) = "hello" printl...
一、定长数组和变长数组
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package com.dzx.listPack
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import scala.collection.mutable.ArrayBuffer
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object ArrayApp extends App {
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//1.定长数组
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val a = new Array[String](5)
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a.length
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a(0) = "hello"
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println(a)
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println(a(0))
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val b = Array("hadoop", "hello", "spark", "hdfs", "mapredurce")
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println(b(0), b(1))
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val c = Array(2, 3, 4, 5, 6, 7, 8, 9)
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println(c.sum) //求和
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println(c.max) //最大值
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println(c.mkString) //转为string
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println(c.mkString(",")) //以逗号隔开的string
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println(c.mkString("<", ",", ">")) // 开始和结束分别是< >
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//2.变长数组
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val d = ArrayBuffer[Int]()
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//追加元素
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d += 1
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d += 2
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//追加多个元素
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d += (3, 4, 5)
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//直接追加一个数组
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d ++= Array(6, 7, 8)
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//在index 为0 的位置添加一个 0元素
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d.insert(0, 0)
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println(c.mkString(","))
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//移除
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d.remove(1)
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d.remove(0, 3)
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//从末尾移除
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d.trimEnd(2)
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d.toArray
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for (i <- 0 until d.length) {
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println(d(i))
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}
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for (ele <- d) {
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println(ele)
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}
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for (i <- (0 until d.length).reverse) {
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println(d(i))
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}
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}
二、定长list，set ，变长list ，set 以及 模式匹配
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object ListApp extends App {
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//list 有序的，可以重复的
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//定长list
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val l = List(11, 2, 3)
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println(l.head)
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println(l.tail)
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Nil // 等于 List()，空的不可变长的集合
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val l2 = 1 :: Nil
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val l3 = 2 :: l2
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val l4 = 1 :: 2 :: 3 :: 4 :: Nil
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//变长list
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val l5 = scala.collection.mutable.ListBuffer[Int]()
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l5 += 2
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l5 += (3, 4, 6)
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l5 ++= List(6, 7, 8, 9)
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l5 -= 2
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l5 -= 3
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l5 -= (1, 4)
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l5 --= List(5, 6, 7, 8)
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println(l5)
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l5.isEmpty
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l5.head
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l5.tail
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l5.tail.head
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def sum(nums: Int*): Int = {
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if (nums.length == 0) {
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0
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} else { //递归
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nums.head + sum(nums.tail: _*) //_* 将nums.tail转换为 可变参数
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}
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}
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println(sum())
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println(sum(1, 2, 3, 4))
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//set 无序的，不重复的
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val s = Set(1, 2, 2, 1, 4, 3)
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println(s) //Set(1, 2, 4, 3)
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val s1 = scala.collection.mutable.Set[Int]()
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s1 += 1
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s1 += (11, 2, 3)
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s1 ++= Set(4, 5, 6)
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//模式匹配
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// match case 类似于 java 中的 switch case
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var names = Array("a", "b", "c");
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val name = names(Random.nextInt(names.length))
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name match {
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case "a" => println("季老师")
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case "b" => println("波老师")
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case _ => println("真不知道你们在说什么。。。")
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}
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//case 不仅仅 可以匹配一个值，还可以加一个if条件进行过滤判断
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//字符串的模式匹配
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def judgeGrade(grade: String, name: String) = {
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grade match {
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case "A" => println("Excellent...")
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case "B" => println("Good ...")
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case "C" => println("just so so...")
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case _ if (name == "lisi") => println(name + ",you are a good boy")
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case _ => println("you need work harder...")
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}
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}
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judgeGrade("f", "lisi")
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//数组的模式匹配
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def greeting(array: Array[String]) = {
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array match {
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case Array("zhangsan") => println("hi:zhangsan")
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case Array(x, y) => println("hi :" + x + "," + y)
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case Array("zhangsan", _*) => println("hi zhangsan and other friends ...")
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case _ => println("hi : everybody ...")
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}
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}
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greeting(Array("zhangsan"))
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//list的模式匹配
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def listMatch(list: List[String]): Unit = {
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list match {
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case "zhangsan" :: Nil => println("hi zhangsan")
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case x :: y :: Nil => println("hi:" + x + "," + y)
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case "zhangsan" :: tail => println("hi :zhangsan and other friends")
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case _ => println("hi :everybody....")
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}
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}
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listMatch(List("lisi"))
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//类型的模式匹配
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def typeMatch(obj: Any): Unit = {
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obj match {
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case x:Int =>println("Int")
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case s:String =>println("String")
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case m:Map[_,_]=>m.foreach(println)
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case _ =>println("other type")
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}
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}
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typeMatch(Map("name"->"pk"))
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//sacla 的异常处理
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try {
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var i = 10 / 0
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println(i)
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}catch{
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case e:ArithmeticException=>println("除数不能为0")
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case e:Exception =>println(e.getMessage())
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}finally {
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//释放资源，一定能执行
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}
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//case class 的模式匹配
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class Person
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case class CTO( name:String,floor:String ) extends Person
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case class Employee( name:String,floor:String ) extends Person
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case class Other( name:String) extends Person
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def caseClassMatch(person: Person): Unit ={
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person match {
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case CTO(name,floor)=> println("cto name is "+name)
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case Employee(name,floor) =>println("employee name is "+name)
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case Other(name) =>println("other name is "+name)
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}
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}
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caseClassMatch(CTO("ctO","5"))
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}
文章来源: blog.csdn.net，作者：血煞风雨城2018，版权归原作者所有，如需转载，请联系作者。
原文链接：blog.csdn.net/qq_31905135/article/details/85072111
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