WordCountB.java Source code

Introduction

Here is the source code for WordCountB.java

Source

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
//package org.apache.hadoop.examples;

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.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Partitioner;
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;

public class WordCountB {

    public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable> {

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

        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
            StringTokenizer itr = new StringTokenizer(value.toString());
            while (itr.hasMoreTokens()) {
                String cur = itr.nextToken();
                // Only count the real words starting with letters "m n o p q"
                // (no matter capitalized)
                if ((cur.charAt(0) >= 'm' && cur.charAt(0) <= 'q')
                        || (cur.charAt(0) >= 'M' && cur.charAt(0) <= 'Q')) {
                    word.set(cur);
                    context.write(word, one);
                }
            }
        }

    }

    /**
     * 
     * @author junrongyan Partitioner class
     *
     */
    public static class Letterpartitioner extends Partitioner<Text, IntWritable> {

        @Override
        public int getPartition(Text key, IntWritable value, int numReduceTasks) {
            String w = key.toString();
            Character w1 = Character.toLowerCase(w.charAt(0));
            //this is done to avoid performing mod with 0
            if (numReduceTasks == 0) {
                return 0;
            }
            // Words starting with "M" or "m" assigned to reduce task 0
            if (w1 == 'm') {
                return 0;
            }
            // Words starting with "N" or "n" assigned to reduce task 1
            if (w1 == 'n') {
                return 1 % numReduceTasks;
            }
            // Words starting with "O" or "o" assigned to reduce task 2
            if (w1 == 'o') {
                return 2 % numReduceTasks;
            }
            // Words starting with "P" or "p" assigned to reduce task 3
            // Else, words starting with "Q" or "q" assigned to reduce task 4
            if (w1 == 'p') {
                return 3 % numReduceTasks;
            } else {
                return 4 % numReduceTasks;
            }
        }

    }

    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();
        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
        if (otherArgs.length < 2) {
            System.err.println("Usage: wordcount <in> [<in>...] <out>");
            System.exit(2);
        }
        Job job = Job.getInstance(conf, "word count");
        job.setJarByClass(WordCountB.class);
        job.setMapperClass(TokenizerMapper.class);
        // Setup the Combiner
        job.setCombinerClass(IntSumReducer.class);
        // Setup the Partitioner
        job.setPartitionerClass(Letterpartitioner.class);
        job.setReducerClass(IntSumReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        for (int i = 0; i < otherArgs.length - 1; ++i) {
            FileInputFormat.addInputPath(job, new Path(otherArgs[i]));
        }
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[otherArgs.length - 1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}