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

  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))
  }
}