Word Count MapReduce Code

 Mapper Logic:

import java.io.IOException;

import java.util.StringTokenizer;

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Mapper;

public class WordCountMapper extends Mapper<LongWritable, Text, Text, IntWritable> {

  @Override

  public void map(LongWritable key, Text value, Context con)

      throws IOException, InterruptedException {

    String line = value.toString();

    String[] words = line.split("\\s");

    for(String s:words) {

                con.write(new Text(s), new IntWritable(1));

    }

  }

}

 

 

Reducer Logic:

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Reducer;

public class WordCountReducer extends Reducer<Text, IntWritable, Text, IntWritable> {

    @Override

  public void reduce(Text key, Iterable<IntWritable> values,Context con)

      throws IOException, InterruptedException {  

                  int sum = 0;

                  for(IntWritable i:values) {

                                  sum = sum + i.get();

                  }

                  con.write(key, new IntWritable(sum));

      }

}

 

 

Driver Logic:

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.lib.input.FileInputFormat;

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

public class WordCountDriver {

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

    if (args.length != 2) {

      System.err.println("Usage: WordCount <input path> <output path>");

      System.exit(-1);

    }

     Job job = new Job();

    job.setJarByClass(WordCountDriver.class);

    job.setJobName("Word Count");

    FileInputFormat.addInputPath(job, new Path(args[0]));

    FileOutputFormat.setOutputPath(job, new Path(args[1]));

    job.setMapperClass(WordCountMapper.class);

    job.setReducerClass(WordCountReducer.class);

    job.setOutputKeyClass(Text.class);

    job.setOutputValueClass(IntWritable.class);

       System.exit(job.waitForCompletion(true) ? 0 : 1);

   }

}