Solution :

Step 1 : Create file in hdfs (We will do using Hue). However, you can first create in local filesystem and then upload it to hdfs.

Step 2 : Load data.csv file from hdfs and create PairRDDs

val name = sc.textFile("spark8/data.csv")

val namePairRDD = name.map(x=> (x.split(",")(0),x.split(",")(1)))

Step 3 : Now swap namePairRDD RDD.

val swapped = namePairRDD.map(item => item.swap)

Step 4 : Now combine the rdd by key.

val combinedOutput = namePairRDD.combineByKey(List(_), (x:List[String], y:String) => y :: x, (x:List[String], y:List[String]) => x ::: y)

Step 5 : Save the output as a Text file and output must be written in a single file. :ombinedOutput.repartition(1).saveAsTextFile("spark8/result.txt")