scala语言入门（三）scala集合

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"
       println(a)
       println(a(0))
        val b = Array("hadoop", "hello", "spark", "hdfs", "mapredurce")
       println(b(0), b(1))
        val c = Array(2, 3, 4, 5, 6, 7, 8, 9)
       println(c.sum) //求和
       println(c.max) //最大值
       println(c.mkString) //转为string
       println(c.mkString(",")) //以逗号隔开的string
       println(c.mkString("<", ",", ">")) // 开始和结束分别是< >
       //2.变长数组
        val d = ArrayBuffer[Int]()
       //追加元素
        d += 1
        d += 2
       //追加多个元素
        d += (3, 4, 5)
       //直接追加一个数组
        d ++= Array(6, 7, 8)
       //在index 为0 的位置添加一个 0元素
        d.insert(0, 0)
       println(c.mkString(","))
       //移除
        d.remove(1)
        d.remove(0, 3)
       //从末尾移除
        d.trimEnd(2)
        d.toArray
       for (i <- 0 until d.length) {
      println(d(i))
        }
       for (ele <- d) {
      println(ele)
        }
       for (i <- (0 until d.length).reverse) {
      println(d(i))
        }
      }
  
 

二、定长list，set ，变长list ，set 以及 模式匹配

      object ListApp extends App {
       //list 有序的，可以重复的
       //定长list
       val l = List(11, 2, 3)
        println(l.head)
        println(l.tail)
       Nil // 等于 List()，空的不可变长的集合
       val l2 = 1 :: Nil
       val l3 = 2 :: l2
       val l4 = 1 :: 2 :: 3 :: 4 :: Nil
       //变长list
       val l5 = scala.collection.mutable.ListBuffer[Int]()
        l5 += 2
        l5 += (3, 4, 6)
        l5 ++= List(6, 7, 8, 9)
        l5 -= 2
        l5 -= 3
        l5 -= (1, 4)
        l5 --= List(5, 6, 7, 8)
        println(l5)
        l5.isEmpty
        l5.head
        l5.tail
        l5.tail.head
       def sum(nums: Int*): Int = {
      if (nums.length == 0) {
      0
       } else { //递归
       nums.head + sum(nums.tail: _*) //_* 将nums.tail转换为 可变参数
       }
        }
        println(sum())
        println(sum(1, 2, 3, 4))
       //set 无序的，不重复的
       val s = Set(1, 2, 2, 1, 4, 3)
        println(s) //Set(1, 2, 4, 3)
       val s1 = scala.collection.mutable.Set[Int]()
        s1 += 1
        s1 += (11, 2, 3)
        s1 ++= Set(4, 5, 6)
       //模式匹配
       // match case 类似于 java 中的 switch case
       var names = Array("a", "b", "c");
       val name = names(Random.nextInt(names.length))
        name match {
      case "a" => println("季老师")
      case "b" => println("波老师")
      case _ => println("真不知道你们在说什么。。。")
        }
       //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
       //字符串的模式匹配
       def judgeGrade(grade: String, name: String) = {
       grade match {
      case "A" => println("Excellent...")
      case "B" => println("Good ...")
      case "C" => println("just so so...")
      case _ if (name == "lisi") => println(name + ",you are a good boy")
      case _ => println("you need work harder...")
       }
        }
        judgeGrade("f", "lisi")
       //数组的模式匹配
       def greeting(array: Array[String]) = {
       array match {
      case Array("zhangsan") => println("hi:zhangsan")
      case Array(x, y) => println("hi :" + x + "," + y)
      case Array("zhangsan", _*) => println("hi zhangsan and other friends ...")
      case _ => println("hi : everybody ...")
       }
        }
        greeting(Array("zhangsan"))
       //list的模式匹配
       def listMatch(list: List[String]): Unit = {
       list match {
      case "zhangsan" :: Nil => println("hi zhangsan")
      case x :: y :: Nil => println("hi:" + x + "," + y)
      case "zhangsan" :: tail => println("hi :zhangsan and other friends")
      case _ => println("hi :everybody....")
       }
        }
        listMatch(List("lisi"))
       //类型的模式匹配
       def typeMatch(obj: Any): Unit = {
       obj match {
      case  x:Int =>println("Int")
      case  s:String =>println("String")
      case  m:Map[_,_]=>m.foreach(println)
      case  _ =>println("other type")
       }
        }
        typeMatch(Map("name"->"pk"))
       //sacla 的异常处理
       try {
       var i = 10 / 0
        println(i)
      }catch{
       case  e:ArithmeticException=>println("除数不能为0")
       case  e:Exception =>println(e.getMessage())
      }finally {
        //释放资源，一定能执行
      }
       //case class 的模式匹配
       class Person
       case class CTO( name:String,floor:String ) extends Person
       case class Employee( name:String,floor:String ) extends Person
       case class Other( name:String) extends Person
       def caseClassMatch(person: Person): Unit ={
       person match {
      case  CTO(name,floor)=> println("cto name is "+name)
      case  Employee(name,floor) =>println("employee name is "+name)
      case Other(name) =>println("other name is "+name)
       }
        }
        caseClassMatch(CTO("ctO","5"))
      }
  
 

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