1回答

• 

  zhaoliang1133

  2016-01-13 14:11:40

  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 WordCountMap extends
              Mapper<LongWritable, Text, Text, IntWritable> {
          private final IntWritable one = new IntWritable(1);
          private Text word = new Text();
  
          public void map(LongWritable key, Text value, Context context)
                  throws IOException, InterruptedException {
              String line = value.toString();
              StringTokenizer token = new StringTokenizer(line);
              while (token.hasMoreTokens()) {
                  word.set(token.nextToken());
                  context.write(word, one);
              }
          }
      }
  
      public static class WordCountReduce extends
              Reducer<Text, IntWritable, Text, IntWritable> {
          public void reduce(Text key, Iterable<IntWritable> values,
                  Context context) throws IOException, InterruptedException {
              int sum = 0;
              for (IntWritable val : values) {
                  sum += val.get();
              }
              context.write(key, new IntWritable(sum));
          }
      }
  
      public static void main(String[] args) throws Exception {
          Configuration conf = new Configuration();
          Job job = new Job(conf);
          job.setJarByClass(WordCount.class);
          job.setJobName("wordcount");
          job.setOutputKeyClass(Text.class);
          job.setOutputValueClass(IntWritable.class);
          job.setMapperClass(WordCountMap.class);
          job.setReducerClass(WordCountReduce.class);
          job.setInputFormatClass(TextInputFormat.class);
          job.setOutputFormatClass(TextOutputFormat.class);
          FileInputFormat.addInputPath(job, new Path(args[0]));
          FileOutputFormat.setOutputPath(job, new Path(args[1]));
          job.waitForCompletion(true);
      }
  }
  
  

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