sort by key for word count problem

Author: James Lee

src/main/java/com/sparkTutorial/pairRdd/sort/sortbykey/SortedWorldCountProblem.java

@@ -0,0 +1,16 @@
+package com.sparkTutorial.pairRdd.sort.sortbykey;
+
+
+public class SortedWorldCountProblem {
+
+    /* TODO: Create a Spark program to read the an article from in/word_count.text, output the number of occurrence of each word in descending order.
+
+       Sample output:
+
+       apple : 200
+       shoes : 193
+       bag : 176
+       ...
+     */
+}
+

src/main/java/com/sparkTutorial/pairRdd/sort/sortbykey/SortedWorldCountSolution.java

@@ -0,0 +1,42 @@
+package com.sparkTutorial.pairRdd.sort.sortbykey;
+
+
+import org.apache.log4j.Level;
+import org.apache.log4j.Logger;
+import org.apache.spark.SparkConf;
+import org.apache.spark.api.java.JavaPairRDD;
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
+import org.apache.spark.api.java.function.Function2;
+import org.apache.spark.api.java.function.PairFunction;
+import scala.Tuple2;
+
+import java.util.Arrays;
+
+public class SortedWorldCountSolution {
+
+    public static void main(String[] args) throws Exception {
+
+        Logger.getLogger("org").setLevel(Level.ERROR);
+        SparkConf conf = new SparkConf().setAppName("wordCounts").setMaster("local[3]");
+        JavaSparkContext sc = new JavaSparkContext(conf);
+
+        JavaRDD<String> lines = sc.textFile("in/word_count.text");
+        JavaRDD<String> wordRdd = lines.flatMap(line -> Arrays.asList(line.split(" ")).iterator());
+
+        JavaPairRDD<String, Integer> wordPairRdd = wordRdd.mapToPair((PairFunction<String, String, Integer>) word -> new Tuple2<>(word, 1));
+
+        JavaPairRDD<String, Integer> wordToCountPairs = wordPairRdd.reduceByKey((Function2<Integer, Integer, Integer>) (x, y) -> x + y);
+
+        JavaPairRDD<Integer, String> countToWordParis = wordToCountPairs.mapToPair((PairFunction<Tuple2<String, Integer>, Integer, String>) wordToCount -> new Tuple2<>(wordToCount._2(), wordToCount._1()));
+
+        JavaPairRDD<Integer, String> sortedCountToWordParis = countToWordParis.sortByKey(false);
+
+        JavaPairRDD<String, Integer> sortedWordToCountPairs = sortedCountToWordParis.mapToPair((PairFunction<Tuple2<Integer, String>, String, Integer>) countToWord -> new Tuple2<>(countToWord._2(), countToWord._1()));
+
+        for (Tuple2<String, Integer> wordToCount : sortedWordToCountPairs.collect()) {
+            System.out.println(wordToCount._1() + " : " + wordToCount._2());
+
+        }
+    }
+}