RT。

package com.scalalearn.scala.main
//java中的List轉為scala buffer至關重要的引入
import scala.collection.JavaConversions.asScalaBuffer
import java.awt.datatransfer.{DataFlavor, SystemFlavorMap}
import scala.collection.mutable.Buffer
import scala.collection.mutable.ArrayBuffer
import scala.util.Random
/**
  * 快學scala 03習題
  */
object LearnScala03 {
  //1.編寫一段程式碼，將a設定為n個隨機整數的陣列，要求隨機數位於[0,n)之間
  def execise1(n:Int):Array[Int] = {
    val random:Random = new Random()
    val randomArr:Array[Int] = new Array[Int](n)
    for(i <- 0 until n) randomArr(i) = random.nextInt(n)
    randomArr
  }

  //2.編寫一個程式，將整數陣列中相鄰的元素置換；例如，Array(1,2,3,4,5)置換後變為Array(2,1,4,3,5)
  def execise2(arr:Array[Int]):Array[Int] = {
    for(i <- Range(0,arr.length/2+1,2)){
      val temp = arr(i)
      arr(i) = arr(i+1)
      arr(i+1) = temp
    }
    arr
  }

  //3.重複前一個練習，不過這一次生成的新的值交換過的陣列，用for/yeild
  def execise3(arr:Array[Int]):Array[Int] = {
    val newArr = for( i <- Range(0,arr.length)) yield {
      if (arr.length % 2 == 1 && i == arr.length - 1) arr(i) else if (i % 2 == 0) arr(i+1) else arr(i-1)
    }
    newArr.toArray
  }

  //4.給定一個整數陣列，產生一個新的陣列，包含原陣列中的所有正值，按原有順序排序
  //之後的元素是所有的零或者負值，按原有順序排序
  def execise4(arr:Array[Int]):Array[Int] = {
    var newArr:Array[Int] = for (elem <- arr if elem > 0) yield elem
    val newArr1:Array[Int] = for (elem <- arr if elem <= 0) yield elem
    newArr ++= newArr1
    newArr
  }

  //5.如何計算Array[Double]的平均值
  def execise5(arr:Array[Double]):Double = {
    arr.sum/arr.length
  }

  //7.寫一個程式，輸出陣列中的所有值，去掉重複項
  def execise7(arr:Array[Int]):Array[Int] = {
    arr.distinct
  }

  //9.建立一個java.util.TimeZone.getAvailableIDs返回的時區的集合，判斷條件是它們在美洲；去掉"America/"字首並排序
  def execise9():Unit = {
    var timezoneArr:Array[String] = java.util.TimeZone.getAvailableIDs()
    var filterArr = for(elem <- timezoneArr if !elem.startsWith("America/")) yield elem
    var sortedArr = filterArr.sorted
    for(elem <- sortedArr) println(elem)
  }

  //10.引入java.awt.datatransfer._並構建一個型別為SystemFlavorMap的物件
  //然後以DataFlavor.imageFlavor為引數呼叫getNativesForFlavor的方法，以Scala緩衝保留返回值
  //為什麼要用這樣一個晦澀難懂的類？因為java標準類庫中很難得到試用java.util.List的程式碼
  def execise10():Unit = {
    val flavors = SystemFlavorMap.getDefaultFlavorMap.asInstanceOf[SystemFlavorMap]
    val buffer:Buffer[String] = flavors.getNativesForFlavor(DataFlavor.imageFlavor)
  }

  def main(args:Array[String]):Unit={
    println("=================execise1=====================")
    val arr1 = LearnScala03.execise1(4)
    for(n <- arr1) print(n+" ")
    println("\n")

    println("=================execise2=====================")
    val arr2 = LearnScala03.execise2(Array(1,2,3,4,5))
    for(n <- arr2) print(n+" ")
    println("\n")

    println("=================execise3=====================")
    val arr3 = LearnScala03.execise3(Array(1,2,3,4,5))
    for(n <- arr3) print(n+" ")
    println("\n")

    println("=================execise4=====================")
    val arr4 = LearnScala03.execise4(Array(3,1,-2,6,0,-1,7))
    for(n <- arr4) print(n+" ")
    println("\n")

    println("=================execise5=====================")
    println(LearnScala03.execise5(Array(1.0,2.0,3.0)))

    println("=================execise6=====================")
    //如何組織Array[Int]使他們反序排列，如果是ArrayBuffer呢？
    val arr61 = Array[Int](1,2,3)
    val arr62 = new Array[Int](arr61.length)
    for(i <- 0 until arr61.length){
      arr62(arr61.length - 1 - i) = arr61(i)
    }
    for(n <- arr62) print(n+" ")
    println("\n")

    val arr63 = ArrayBuffer(1,2,3)
    val arr64 = arr63.reverse
    for(n <- arr64) print(n+" ")
    println("\n")

    println("=================execise7=====================")
    val arr7 = LearnScala03.execise7(Array(1,3,1,2,4,2))
    for(n <- arr7) print(n+" ")
    println("\n")

    //第8題看不懂題意

    println("=================execise9=====================")
    LearnScala03.execise9()
  }
}