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Run Word Count Java Mapreduce Program in Hadoop

Jan 20, 2020 Word Count, Hadoop, Mapreduce, 10131 Views
In This Article, we'll discuss Run Word Count Java Mapreduce Program in Hadoop

How to create Jar file for Wordcount using eclipse IDE for Java.

1:- Create a Java project in Eclipse with name “WordCount”

2:- Create a class file named “WordCount.java” in src folder.

3:- Download hadoop-core.jar and hadoop-commons.jar.

4:-Right click on “WordCount” project -> Click on properties ->; Click on “;Java Build Path”-> Click on tab – “Libraries” -> Add External jars



5:-Select hadoop-core.jar. Click Apply and Close


6:- Add "Mapper", "Reducer" and "Driver" code to WordCount.java

import java.io.IOException;

import java.io.InvalidObjectException;

import java.util.StringTokenizer;

import java.util.Iterator;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Job;

import org.apache.hadoop.mapreduce.Mapper;

import org.apache.hadoop.mapreduce.Reducer;

import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class WordCountDemo


public static class TokenizerMapper

extends Mapper<Object, Text, Text, IntWritable>


private final static IntWritable one = new IntWritable(1); private Text word = new Text();

public void map(Object key, Text value, Context context) throws IOException, InterruptedException


     StringTokenizer itr = new StringTokenizer(value.toString());

     while (itr.hasMoreTokens())



      context.write(word, one);




public static class IntSumReducer

extends Reducer<Text,IntWritable,Text,IntWritable>


     private IntWritable result = new IntWritable();

    public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException


    int sum = 0;

    for (IntWritable val : values)


        sum += val.get();


       result.set(sum); context.write(key, result);



public static void main(String[] args) throws Exception


Configuration conf = new Configuration(); conf job = new conf();

//Job job = Job.getInstance(conf, "word count"); job.setJarByClass(WordCountDemo.class); job.setMapperClass(TokenizerMapper.class); job.setCombinerClass(IntSumReducer.class); job.setReducerClass(IntSumReducer.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); FileInputFormat.addInputPath(job, new Path(args[0])); FileOutputFormat.setOutputPath(job, new Path(args[1])); System.exit(job.waitForCompletion(true) ? 0 : 1);



7:-Compile the project.

8:- Right click on project -> Export -> Jar -> Add location and name of jar.





 9:- when jar file will be created go to Hadoop exp copy the file and open terminal when all the services of the Hadoop get started choose the file which want to count the words


10:-show the content of the file


11:- run command to word count of the file

   hadoop jar wordCount.jar wordCount 

12 :- after the program get executed the output will show like this









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