pair RDD groupByKey countByKey countByValue aggregateByKey reduceByKey 测试
vald=sc.makeRDD(Array(1,2,3,4,5,1,3,5))
valdd=d.map(x=>(x,1))//构造pairRDD,dd:RDD[(Int,Int)]
1.groupByKey
valdg=dd.groupByKey()//dg:RDD[(Int,Iterable[Int])]
valdgc=dg.collectAsMap//dgc:Map[Int,Iterable[