用scala實現Spark的RDD接口

import org.apache.spark.SparkConf
import org.apache.spark.SparkContext
import org.apache.spark.rdd.RDD

object Spark {
  final val conf:SparkConf=new SparkConf().setAppName("Spark").setMaster("local")
  final val sc:SparkContext=new SparkContext(conf)
  //利用scala實現Spark的接口
   def main (args:Array[String]):Unit={

     val arr3=Array("dd","aa","cc")
     val arr0=arr3.map(x=>x.substring(0,1))

     //filter 過濾元素
     val arr4=arr3.filter(x=>x=="aa")
     //show(arr2)
     //flatMap
     val str5=Array("張無忌 宋青書","張媛媛 宋佳")
     val st6=str5.flatMap(x=>x.split(" "))
     show(st6)
     val str7=str5.map("hello "+_)
     //show(str7)
     //mapPartitions
     val ap11=Array(1,5,21,64,1,77,42,4)
     val list11: List[Int] = ap11.toList
     val rdd011=sc.parallelize(list11,3)//通過sparkContext創建PDD
     //rdd011.collect().map(println(_))
     //需要用到collect纔會數據落地
     //遍歷rdd01
     //mapPartitions
     //的用處是每次處理一個分區的數據
     //println("----mapPartition-----")
     //mapPartitions()


     //map
     val arr=Array("dd","aa","cc")
     val arr1=arr.map(x=>x.substring(0,1))
     for(i<-arr1) println(i)
     //filter 過濾元素
     val arr2=arr.filter(x=>x=="aa")
     //show(arr2)
     //flatMap
     val str1=Array("張無忌 宋青書","張媛媛 宋佳")
     val st2=str1.flatMap(x=>x.split(" "))
     show(st2)
     val str3=st2.map("hello "+_)
     show(str3)
     //mapPartitions
     val ap=Array(1,5,21,64,1,77,42,4)
     val list: List[Int] = ap.toList
     val rdd01=sc.parallelize(list,3)//通過sparkContext創建PDD
     rdd01.collect().map(println(_))
     //需要用到collect纔會數據落地
     //遍歷rdd01
     //mapPartitions
     //的用處是每次處理一個分區的數據
     println("----mapPartition-----")
    mapPartitions()
     //println("----sample-----")
     //sample()
     //println("----union-----")
     //union()
     /*println("---intersection---")
     intersection()
     println("---disinct---")
     distinct()*/
     /*println("___cartesian___")
     cartesian()*/
     /*println("___repartition___")
     repartition()
     println("___repartitionAndSortWithinPartitions___")
     repartitionAndSortWithinPartitions()*/
     /*println("__------cogroup-------")
     cogroup
     println("__------aggregateByKey-------")
     aggregateByKey*/
     join
   }
  //打印
  def show(arr:Array[String]):Unit={
    for(i<-arr) print(i+" ")
    println()
  }
  def mapPartitions():Unit={
    val ll:List[Int]=List(1,2,3,4,5,6)
    val rdd01=sc.parallelize(ll,2)

    var rdd02=rdd01.mapPartitions(doubleP)
    println(rdd02.collect().mkString)
  }
  final def doubleP(iter:Iterator[Int]):Iterator[(Int,Int)]={
    var res=List[(Int,Int)]()
    //定義一個空的LiST接收結果
    while(iter.hasNext){
      val cur=iter.next()
      res.::=(cur,cur*2)
    }
    res.iterator
  }


  //sample
  //有放回取樣
  //無放回取樣
  def sample():Unit={
    var listA:List[Int]=Array(1,3,5,13,56,31,44,12,33,2).toList
    //創建list
    var rdd01=sc.parallelize(listA)
    var random=rdd01.sample(false,0.5)//每個概率爲0.1 所以代表取5個
    println(random.map(x=>" "+x).collect().mkString)
  }

  def union():Unit={
    var list1=List(1,3,5,6)
    var list2=List(1,5,2,1,4)
    var rdd1=sc.parallelize(list1)
    var rdd2=sc.parallelize(list2)
    var ui=rdd1.union(rdd2)
    print(ui.map(x=>" "+x).collect().mkString)
  }
  def intersection():Unit={//求交集
    var list1=List(1,3,5,6)
    var list2=List(1,5,2,1,4)
    var rdd1=sc.parallelize(list1)
    var rdd2=sc.parallelize(list2)
    var in=rdd1.intersection(rdd2)
    print(in.map(x=>" "+x).collect().mkString)
  }

  def distinct():Unit={//去重
    var list2=List(1,5,2,1,4,6,6,3,2,1,3,4,5,1)
    var rdd2=sc.parallelize(list2)
    var in=rdd2.distinct()
    print(in.map(x=>" "+x).collect().mkString)
  }

  def cartesian():Unit={//笛卡爾積
    var list1=List(1,3,5,6)
    var list2=List(1,5,2,1,4)
    var rdd1=sc.parallelize(list1)
    var rdd2=sc.parallelize(list2)
    var dikaer=rdd1.cartesian(rdd2)
    println(dikaer.map(" "+_).collect().mkString)
  }
  /**
    * 進行重分區
    * HDFS -》 hello.txt   2個文件塊（不包含副本）
    * 2個文件塊 -》2個分區  -》當spark任務運行，一個分區就啓動一個task任務。
    *
    * 解決的問題：本來分區數少  -》 增加分區數
    */
  def repartition():Unit={
    var list2=List(1,5,2,1,4,1,3,5,6,12,13,14,15,16)
    var rdd2=sc.parallelize(list2,1)
    var rdd3=rdd2.repartition(4)
    println(rdd3.map(" "+_).collect().mkString)
  }

  def repartitionAndSortWithinPartitions():Unit={
    var list2=List(1,5,2,1,4,1,3,5,6,12,13,14,15,16)
    var rdd2=sc.parallelize(list2,1)
    println(rdd2.repartition(4).map(" "+_).sortBy(x=>x).collect().mkString)
    var rdd3=rdd2.repartition(4).map(" "+_).sortBy(x=>x)
    println("把分區變少")
    var rdd4=rdd3.coalesce(1)
    println(rdd4.sortBy(x=>x).collect().mkString)
  }

  def cogroup:Unit={//將兩個tuple或者map的一個鍵作爲關聯
    var arr1=Array(
      ("1","李小龍"),("2","刀劍笑"),("3","蜘蛛俠")
    )
    var arr2=Array(
      ("1","雙節棍"),("2","赤血劍"),("3","危急感官")
    )
    var rdd1=sc.parallelize(arr1)
    var rdd2=sc.parallelize(arr2)
    val unit: RDD[(String, (Iterable[String], Iterable[String]))] = rdd1.cogroup(rdd2)
    unit.foreach(println)//不需要像下面的寫法也能遍歷
    //x=>println(x._1+"---"+x._2._1+"|"+x._2._2)//
  }
  def aggregateByKey():Unit={//scala是沒有mapToPair函數的，scala版本只需要map就可以了
    var str=Array("marry i marry who","who will marry you i ?")
    var sup=str.map(x=>x.split(" ")).flatten.map(x=>(x,1)).groupBy(x=>x._1).map(x=>(x._1,x._2.length)).toList.sortBy(x=>x._2).reverse
    print(sup.map(x=>x))
  }
  def join():Unit={
    var arr1=Array(
      ("1",23),("2",11),("3",22)
    )
    var arr2=Array(
      ("1","雙節棍"),("2","赤血劍"),("3","危急感官"),("2","天地無雙劍")
    )
    var rdd1=sc.parallelize(arr1)
    var rdd2=sc.parallelize(arr2)
    var join=rdd1.join(rdd2)
    var join1=rdd1.reduceByKey((x,y)=>x+y)
    println(join1)
    println(join.map(x=>"+++++"+x._1+"--"+x._2._1+"--"+x._2._2).collect().mkString)
  }
}