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November 23, 2010 16:27
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| /** | |
| * WordCount.java - the very-first MapReduce Program | |
| * | |
| * <h1>How To Compile</h1> | |
| * export HADOOP_HOME=/usr/lib/hadoop-0.20/ | |
| * export DIR=wordcount_classes | |
| * rm -fR $DIR | |
| * mkdir $DIR | |
| * javac -classpath ${HADOOP_HOME}/hadoop-core.jar -d $DIR WordCount.java | |
| * jar -cvf wordcount.jar -C $DIR . | |
| */ | |
| package net.kzk9; | |
| 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.input.TextInputFormat; | |
| import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; | |
| import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat; | |
| public class WordCount { | |
| public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> { | |
| private final static IntWritable one = new IntWritable(1); | |
| private Text word = new Text(); | |
| @Override | |
| protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { | |
| String line = value.toString(); | |
| StringTokenizer tokenizer = new StringTokenizer(line); | |
| while (tokenizer.hasMoreTokens()) { | |
| word.set(tokenizer.nextToken()); | |
| context.write(word, one); | |
| } | |
| } | |
| } | |
| public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> { | |
| private IntWritable value = new IntWritable(0); | |
| @Override | |
| protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { | |
| int sum = 0; | |
| for (IntWritable value : values) | |
| sum += value.get(); | |
| value.set(sum); | |
| context.write(key, value); | |
| } | |
| } | |
| public static void main(String[] args) throws Exception { | |
| Configuration conf = new Configuration(); | |
| Job job = new Job(conf, "wordcount"); | |
| job.setJarByClass(WordCount.class); | |
| job.setOutputKeyClass(Text.class); | |
| job.setOutputValueClass(IntWritable.class); | |
| job.setMapperClass(Map.class); | |
| job.setReducerClass(Reduce.class); | |
| job.setInputFormatClass(TextInputFormat.class); | |
| job.setOutputFormatClass(TextOutputFormat.class); | |
| job.setNumReduceTasks(1); | |
| FileInputFormat .setInputPaths(job, new Path(args[0])); | |
| FileOutputFormat.setOutputPath(job, new Path(args[1])); | |
| boolean success = job.waitForCompletion(true); | |
| System.out.println(success); | |
| } | |
| } |
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