Question

Assume our RDD has the following content,

k101 "value-001"

k200 "value-002"

k200 "value-003"

k103 "value-004"

k200 "value-005"

k101 "value-006"

k103 "value-007"

where on each line, the first part is a key (for example, k101), the second part is the value for that key (for example, value-001). What would be the content of myRDD, after running the following code?

JavaPairRDD<String, ArrayList<String>> myRDD = rdd.mapToPair(new

PairFunction<String,String,ArrayList<String>>() {

      public Tuple2<String,ArrayList<String>> call(String line) throws Exception {

         String[] split = line.split(" "); // use space to break the input line

         ArrayList<String> s = new ArrayList<String>();

         return new Tuple2(split[0],

                          new ArrayList( Arrays.asList(new String[]{split[1]}) ) );

      }

}).reduceByKey(new Function2<ArrayList<String>, ArrayList<String>,

ArrayList<String>>() {

public ArrayList<String> call(ArrayList<String> s1, ArrayList<String> s2)

      throws Exception {

            s1.addAll(s2);

            return s1;

      }

});

Answer 1

RDD will contain a list of tuple

with keys as k101,k200,etc but value will be a list

Output

List<Tuple> -->
Value of RDD
k101 -> ["value-001","value-006"]
k200 -> ["value-002","value-003","value-005"]
k103 -> ["value-004","value-007"]​