MapReduce Character Count

 Mapper Logic :

import java.io.IOException;

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 CharCountMapper extends Mapper<LongWritable, Text, Text, IntWritable> {

  @Override

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

      throws IOException, InterruptedException {

    String line = value.toString();

    char[] chars = line.toCharArray();

    for(char c:chars) {

    con.write(new Text("Total Characters"), 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 CharCountReducer extends Reducer<Text, IntWritable, Text, IntWritable> {

  /*

   * bigdata   <1>

   */

  @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 CharCountDriver {

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

    if (args.length != 2) {

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

      System.exit(-1);

    }

    @SuppressWarnings("deprecation")

Job job = new Job();

    job.setJobName("Char Count");

    job.setJarByClass(CharCountDriver.class);

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

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

    job.setMapperClass(CharCountMapper.class);

    job.setReducerClass(CharCountReducer.class);

    job.setOutputKeyClass(Text.class);

    job.setOutputValueClass(IntWritable.class);

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

   }

}