Dinesh on Java

package com.doj.hadoop.driver;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;

/**
 * @author Dinesh Rajput
 *
 */
public class WordCount extends Configured implements Tool {
 @Override
 public int run(String[] args) throws Exception {
   if (args.length != 2) {
       System.err.printf("Usage: %s [generic options] <input> <output>n",
       getClass().getSimpleName());
       ToolRunner.printGenericCommandUsage(System.err);
       return -1;
    }
   JobConf conf = new JobConf(WordCount.class);
   conf.setJobName("Word Count");
   FileInputFormat.addInputPath(conf, new Path(args[0]));
   FileOutputFormat.setOutputPath(conf, new Path(args[1]));
   conf.setMapperClass(WordMapper.class);
   conf.setCombinerClass(WordReducer.class);
   conf.setReducerClass(WordReducer.class);
   conf.setOutputKeyClass(Text.class);
   conf.setOutputValueClass(IntWritable.class);
   return conf.waitForCompletion(true) ? 0 : 1;
 }
 public static void main(String[] args) throws Exception {
   int exitCode = ToolRunner.run(new WordCount(), args);
   System.exit(exitCode);
 }
}

2. MapperCode (WordMapper.java)

package com.doj.hadoop.driver;

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.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;

/**
 * @author Dinesh Rajput
 *
 */
public class WordMapper extends MapReduceBase implements Mapper<LongWritable, Text, Text, IntWritable>
{
 private final static IntWritable one = new IntWritable(1);
 
 private Text word = new Text();
 
 public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter)
  throws IOException
  {
  String line = value.toString();
  StringTokenizer tokenizer = new StringTokenizer(line);
  while (tokenizer.hasMoreTokens())
  {
   word.set(tokenizer.nextToken());
   output.collect(word, one);
   }
  }
}

3. ReducedCode (WordReducer.java)

package com.doj.hadoop.driver;

/**
 * @author Dinesh Rajput
 *
 */
import java.io.IOException;
import java.util.Iterator;
 
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
 
public class WordReducer extends MapReduceBase implements Reducer<Text, IntWritable, Text, IntWritable>
{
 public void reduce(Text key, Iterator<IntWritable> values, OutputCollector<Text, IntWritable> output,
   Reporter reporter) throws IOException
  {
  int sum = 0;
  while (values.hasNext())
  {
   sum += values.next().get();
  }
  output.collect(key, new IntWritable(sum));
  }
}