mapreduce的countWord程序

 

import java.io.IOException;

import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.LongWritable;

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 WordCount {

    public static class TokenizerMapper extends

            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, Context context)

                throws IOException, InterruptedException {

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

            while (itr.hasMoreTokens()) {

                word.set(itr.nextToken());

                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();

        if (args.length != 2) {

            System.err.println("Usage: wordcount  ");

            System.exit(2);

        }



        Job job = new Job(conf, "word count");

        job.setJarByClass(WordCount.class);

        job.setMapperClass(TokenizerMapper.class);

        job.setReducerClass(IntSumReducer.class);

        job.setMapOutputKeyClass(Text.class);

        job.setMapOutputValueClass(IntWritable.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);



    }



}

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