hadoop mapreduce 计算平均气温的代码，绝对原创

1901    46
1902    21
1903    48
1904    33
1905    43
1906    47
1907    31
1908    28
1909    26
1910    35
1911    30
1912    16
1913    29
1914    29
1915    5
1916    21
1917    22
1918    31
1919    27
1920    43
1921    34
1922    27
1923    26

以上为结果

package com.teset;

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.FloatWritable;
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.output.FileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class AvgTemprature extends Configured implements Tool {

 public static class AvgMapper extends
   Mapper<LongWritable, Text, Text, IntWritable> {

  @Override
  protected void map(LongWritable key, Text value,
    Mapper<LongWritable, Text, Text, IntWritable>.Context context)
    throws IOException, InterruptedException {
   // map处理数据
   String str = value.toString();
   String year = null;
   int temprature = 0;
   StringTokenizer tokenstr = new StringTokenizer(str);
   int i = 0;
   while (tokenstr.hasMoreTokens()) {
    String tempstr = tokenstr.nextToken();
    i++;
    if (i == 1) {
     year = tempstr;
     continue;
    } else if (i == 5 && Integer.parseInt(tempstr) != -9999) {
     temprature = Integer.parseInt(tempstr);
     context.write(new Text(year), new IntWritable(temprature));
     break;
    }

   }

  }

 }

 public static class AvgReducer extends
   Reducer<Text, IntWritable, Text, IntWritable> {

  @Override
  protected void reduce(Text key, Iterable<IntWritable> values,
    Reducer<Text, IntWritable, Text, IntWritable>.Context context)
    throws IOException, InterruptedException {
   int sum=0;
   int count=0;
   for (IntWritable value : values) {
    sum=sum+value.get();
    count++;
   }
   if (count!=0){
   context.write(key, new IntWritable(sum/count));
   }
  }

 }

 public static void main(String[] args) throws Exception {
  int res = ToolRunner.run(new Configuration(), new AvgTemprature(), args);
  System.exit(res);
 }

 @Override
 public int run(String[] arg0) throws Exception {
  Configuration conf = getConf();
  Job job = new Job(conf, "AvgTem");// 任务名
  job.setJarByClass(AvgTemprature.class);// 指定class
  // 输入和输出流
  job.setMapperClass(AvgMapper.class);// map
  job.setReducerClass(AvgReducer.class);
  FileInputFormat.addInputPath(job, new Path(arg0[0]));
  FileOutputFormat.setOutputPath(job, new Path(arg0[1]));
  job.setCombinerClass(AvgReducer.class);
  job.setOutputValueClass(IntWritable.class);
  job.setOutputKeyClass(Text.class);
  job.waitForCompletion(true);
  return job.isSuccessful() ? 0 : 1;

 }
}

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