hadoop权威指南第二章示例

import java.io.IOException;

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.mapred.Reporter;
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 MaxTemperature {
 static class MaxTemperatureMapper extends Mapper<LongWritable, Text, Text, IntWritable>{
private  static final int MISSING = 9999;

public void map(LongWritable key, Text value,
  Context context)
  throws IOException, InterruptedException {
 // TODO Auto-generated method stub
 String line = value.toString(); //get as string
 String year = line.substring(5,9); //year
 int airTemperature = Integer.parseInt(line.substring(15,19)); //get temperature to Dec
 
 if (airTemperature != MISSING){
  context.write(new Text(year), new IntWritable(airTemperature));   
 }
}
}
 

static class MaxTemperatureReducer extends Reducer<Text, IntWritable, Text, IntWritable> {

 public void reduce(Text key, Iterable<IntWritable> values,
   Context context, Reporter reporter)
   throws IOException, InterruptedException {
  // TODO Auto-generated method stub
  System.out.println("reducer");
  int maxValue = Integer.MIN_VALUE;
  for (IntWritable value : values){
   maxValue = Math.max(maxValue, value.get());
  }
  context.write(key, new IntWritable(maxValue));
 }

}

 public static void main(String[] args) throws IOException {
  // TODO Auto-generated method stub
  Configuration conf = new Configuration();
  if (args.length !=2){  //judge arg number
   System.err.println("usage: MaxTemperature <input path> <output path>");
   System.exit(-1);
  }
  
  //Job job = new Job();
  Job job = new Job(conf, "NCDC");
  job.setJarByClass(MaxTemperature.class);
  
  FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

  
  job.setMapperClass(MaxTemperatureMapper.class);
  job.setCombinerClass(MaxTemperatureReducer.class);
  job.setReducerClass(MaxTemperatureReducer.class);
  
  job.setOutputKeyClass(Text.class);
  job.setOutputValueClass(IntWritable.class);
  
  try {
   System.exit(job.waitForCompletion(true) ? 0 : 1);
  } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (ClassNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  
  
 }

}

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数据集sample.txt

aaaaa1990aaaaaa0039a
bbbbb1991bbbbbb0040a
ccccc1992cccccc0040c
ddddd1993dddddd0043d
eeeee1994eeeeee0041e
aaaaa1990aaaaaa0031a
bbbbb1991bbbbbb0020a
ccccc1992cccccc0030c
ddddd1993dddddd0033d
eeeee1994eeeeee0031e
aaaaa1990aaaaaa0041a
bbbbb1991bbbbbb0040a
ccccc1992cccccc0040c
ddddd1993dddddd0043d
eeeee1994eeeeee0041e
aaaaa1990aaaaaa0044a
bbbbb1991bbbbbb0045a
ccccc1992cccccc0041c
ddddd1993dddddd0023d
eeeee1994eeeeee0041e

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谁能帮我看看，为什么Reduce没有执行呢？如何修正？