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The following page has been changed by SuzanneMatthews: http://wiki.apache.org/hadoop/WordCount The comment on the change is: added standard wordcount example to this page ------------------------------------------------------------------------------ Word count supports generic options : see DevelopmentCommandLineOptions + Below is the standard wordcount example implemented in Java: + + + {{{#!java + package org.myorg; + + import java.io.IOException; + import java.util.*; + + import org.apache.hadoop.fs.Path; + import org.apache.hadoop.conf.*; + import org.apache.hadoop.io.*; + import org.apache.hadoop.mapred.*; + import org.apache.hadoop.util.*; + + public class WordCount { + + public static class Map 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); + } + } + } + + public static class Reduce 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)); + } + } + + public static void main(String[] args) throws Exception { + JobConf conf = new JobConf(WordCount.class); + conf.setJobName("wordcount"); + + conf.setOutputKeyClass(Text.class); + conf.setOutputValueClass(IntWritable.class); + + conf.setMapperClass(Map.class); + conf.setCombinerClass(Reduce.class); + conf.setReducerClass(Reduce.class); + + conf.setInputFormat(TextInputFormat.class); + conf.setOutputFormat(TextOutputFormat.class); + + FileInputFormat.setInputPaths(conf, new Path(args[0])); + FileOutputFormat.setOutputPath(conf, new Path(args[1])); + + JobClient.runJob(conf); + } + + } + }}} +
