hadoop fs -mkdir /user/joe/wordcount/input

mkdir /home/chenyun/data/mapreduce

cd /home/chenyun/data/mapreduce
touch file01

Hello World, Bye World!

cd /home/chenyun/data/mapreduce

touch file02 vi file02

Hello Hadoop, Goodbye to hadoop.

hadoop fs -put /home/chenyun/data/mapreduce/file01 /user/joe/wordcount/input 

hadoop fs -put /home/chenyun/data/mapreduce/file02 /user/joe/wordcount/input

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

import java.net.URI;

import java.util.ArrayList;

import java.util.HashSet;

import java.util.List;

import java.util.Set;

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.Text;

import org.apache.hadoop.mapreduce.Counter;

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;

import org.apache.hadoop.util.GenericOptionsParser;

import org.apache.hadoop.util.StringUtils;

public class WordCount {

	public static class TokenizerMapper extends

			Mapper<Object, Text, Text, IntWritable> {

		static enum CountersEnum {

			INPUT_WORDS

		}

		private final static IntWritable one = new IntWritable(1);

		private Text word = new Text();

		private boolean caseSensitive;

		private Set<String> patternsToSkip = new HashSet<String>();

		private Configuration conf;

		private BufferedReader fis;

		@Override

		public void setup(Context context) throws IOException,

				InterruptedException {

			conf = context.getConfiguration();

			caseSensitive = conf.getBoolean("wordcount.case.sensitive", true);

			if (conf.getBoolean("wordcount.skip.patterns", false)) {

				URI[] patternsURIs = Job.getInstance(conf).getCacheFiles();

				for (URI patternsURI : patternsURIs) {

					Path patternsPath = new Path(patternsURI.getPath());

					String patternsFileName = patternsPath.getName().toString();

					parseSkipFile(patternsFileName);

				}

			}

		}

		private void parseSkipFile(String fileName) {

			try {

				fis = new BufferedReader(new FileReader(fileName));

				String pattern = null;

				while ((pattern = fis.readLine()) != null) {

					patternsToSkip.add(pattern);

				}

			} catch (IOException ioe) {

				System.err

						.println("Caught exception while parsing the cached file '"

								+ StringUtils.stringifyException(ioe));

			}

		}

		@Override

		public void map(Object key, Text value, Context context)

				throws IOException, InterruptedException {

			String line = (caseSensitive) ? value.toString() : value.toString()

					.toLowerCase();

			for (String pattern : patternsToSkip) {

				line = line.replaceAll(pattern, "");

			}

			StringTokenizer itr = new StringTokenizer(line);

			while (itr.hasMoreTokens()) {

				word.set(itr.nextToken());

				context.write(word, one);

				Counter counter = context.getCounter(

						CountersEnum.class.getName(),

						CountersEnum.INPUT_WORDS.toString());

				counter.increment(1);

			}

		}

	}

	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();

		GenericOptionsParser optionParser = new GenericOptionsParser(conf, args);

		String[] remainingArgs = optionParser.getRemainingArgs();

		if ((remainingArgs.length != 2) && (remainingArgs.length != 4)) {

			System.err

					.println("Usage: wordcount <in> <out> [-skip skipPatternFile]");

			System.exit(2);

		}

		Job job = Job.getInstance(conf, "word count");

		job.setJarByClass(WordCount.class);

		job.setMapperClass(TokenizerMapper.class);

		job.setCombinerClass(IntSumReducer.class);

		job.setReducerClass(IntSumReducer.class);

		job.setOutputKeyClass(Text.class);

		job.setOutputValueClass(IntWritable.class);

		List<String> otherArgs = new ArrayList<String>();

		for (int i = 0; i < remainingArgs.length; ++i) {

			if ("-skip".equals(remainingArgs[i])) {

				job.addCacheFile(new Path(remainingArgs[++i]).toUri());

				job.getConfiguration().setBoolean("wordcount.skip.patterns",

						true);

			} else {

				otherArgs.add(remainingArgs[i]);

			}

		}

		FileInputFormat.addInputPath(job, new Path(otherArgs.get(0)));

		FileOutputFormat.setOutputPath(job, new Path(otherArgs.get(1)));

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

	}

}

hadoop jar /home/chenyun/project/mapreduce/mapreduce.jar com.accp.mapreduce.WordCount /user/joe/wordcount/input /user/joe/wordcount/output

hadoop fs -cat /user/joe/wordcount/output/part-r-00000

\.

\,

\!

to

hadoop fs -put /home/chenyun/data/mapreduce/patterns.txt /user/joe/wordcount

hadoop jar /home/chenyun/project/mapreduce/mapreduce.jar com.accp.mapreduce.WordCount -Dwordcount.case.sensitive=true /user/joe/wordcount/input /user/joe/wordcount/output1 -skip /user/joe/wordcount/patterns.txt

hadoop fs -cat /user/joe/wordcount/output1/part-r-00000

hadoop jar /home/chenyun/project/mapreduce/mapreduce.jar com.accp.mapreduce.WordCount -Dwordcount.case.sensitive=false /user/joe/wordcount/input /user/joe/wordcount/output5 -skip /user/joe/wordcount/patterns.txt

hadoop fs -cat /user/joe/wordcount/output5/part-r-00000