1、项目名称：

2、程序代码：

package com.averagescorecount;

import java.io.IOException;

import java.util.Iterator;

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.output.FileOutputFormat;

public class ScoreCount {

    /*这个map的输入是经过InputFormat分解过的数据集，InputFormat的默认值是TextInputFormat，它针对文件，

    *按行将文本切割成InputSplits，并用LineRecordReader将InputSplit解析成<key,value>对，

    *key是行在文本中的位置，value是文件中的一行。

    */

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

        public void map(LongWritable key , Text value , Context context ) throws IOException, InterruptedException{

            String line = value.toString();

            System.out.println("line:"+line);

            System.out.println("TokenizerMapper.map...");

            System.out.println("Map key:"+key.toString()+" Map value:"+value.toString());

            //将输入的数据首先按行进行分割

            StringTokenizer tokenizerArticle = new StringTokenizer(line,"\n");

            //分别对每一行进行处理

            while (tokenizerArticle.hasMoreTokens()) {

                //每行按空格划分

                StringTokenizer tokenizerLine = new StringTokenizer(tokenizerArticle.nextToken());

                String strName = tokenizerLine.nextToken();//学生姓名部分

                String  strScore= tokenizerLine.nextToken();//成绩部分

                Text name = new Text(strName);

                int scoreInt = Integer.parseInt(strScore);

                 System.out.println("name:"+name+"  scoreInt:"+scoreInt);

                context.write(name, new IntWritable(scoreInt));

                System.out.println("context_map:"+context.toString());

            }

             System.out.println("context_map_111:"+context.toString());

        }

    }

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

            public void reduce(Text key , Iterable<IntWritable> values,Context context) throws IOException,InterruptedException{

                int sum = 0;

                int count = 0;

                int score = 0;

                System.out.println("reducer...");

                System.out.println("Reducer key:"+key.toString()+"  Reducer values:"+values.toString());

                //设置迭代器

                Iterator<IntWritable> iterator = values.iterator();

                while (iterator.hasNext()) {

                    score = iterator.next().get();

                    System.out.println("score:"+score);

                    sum += score;

                    count++;

                }

                int average = (int) sum/count;

                System.out.println("key"+key+"   average:"+average);

                context.write(key, new IntWritable(average));

                System.out.println("context_reducer:"+context.toString());

            }

    }

    public static void main(String[] args) throws Exception {

    Configuration conf = new Configuration();

    Job job = new Job(conf, "score count");

    job.setJarByClass(ScoreCount.class);

    job.setMapperClass(Map.class);

    job.setCombinerClass(Reduce.class);

    job.setReducerClass(Reduce.class);

    job.setOutputKeyClass(Text.class);

    job.setOutputValueClass(IntWritable.class);

    FileInputFormat.addInputPath(job, new Path(args[0]));

    FileOutputFormat.setOutputPath(job, new Path(args[1]));

    System.exit(job.waitForCompletion(true) ? 0 : 1);

    }

}
 
3、测试数据：
陈洲立 67
陈东伟 90
李宁 87
杨森 86
陈东奇 78
谭果 94
盖盖 83
陈洲立 68
陈东伟 96
李宁 82
杨森 85
陈东奇 72
谭果 97
盖盖 82
陈洲立 46
陈东伟 48
李宁 67
杨森 33
陈东奇 28
谭果 78
盖盖 87
 

4、运行过程：

14/09/20 19:31:16 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
14/09/20 19:31:16 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
14/09/20 19:31:16 WARN mapred.JobClient: No job jar file set.  User classes may not be found. See JobConf(Class) or JobConf#setJar(String).
14/09/20 19:31:16 INFO input.FileInputFormat: Total input paths to process : 1
14/09/20 19:31:16 WARN snappy.LoadSnappy: Snappy native library not loaded
14/09/20 19:31:16 INFO mapred.JobClient: Running job: job_local_0001
14/09/20 19:31:16 INFO util.ProcessTree: setsid exited with exit code 0
14/09/20 19:31:16 INFO mapred.Task:  Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@4080b02f
14/09/20 19:31:16 INFO mapred.MapTask: io.sort.mb = 100
14/09/20 19:31:16 INFO mapred.MapTask: data buffer = 79691776/99614720
14/09/20 19:31:16 INFO mapred.MapTask: record buffer = 262144/327680
line:陈洲立 67
TokenizerMapper.map...
Map key:0 Map value:陈洲立 67
name:陈洲立  scoreInt:67
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:陈东伟 90
TokenizerMapper.map...
Map key:13 Map value:陈东伟 90
name:陈东伟  scoreInt:90
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:李宁 87
TokenizerMapper.map...
Map key:26 Map value:李宁 87
name:李宁  scoreInt:87
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:杨森 86
TokenizerMapper.map...
Map key:36 Map value:杨森 86
name:杨森  scoreInt:86
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:陈东奇 78
TokenizerMapper.map...
Map key:46 Map value:陈东奇 78
name:陈东奇  scoreInt:78
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:谭果 94
TokenizerMapper.map...
Map key:59 Map value:谭果 94
name:谭果  scoreInt:94
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:盖盖 83
TokenizerMapper.map...
Map key:69 Map value:盖盖 83
name:盖盖  scoreInt:83
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:陈洲立 68
TokenizerMapper.map...
Map key:79 Map value:陈洲立 68
name:陈洲立  scoreInt:68
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:陈东伟 96
TokenizerMapper.map...
Map key:92 Map value:陈东伟 96
name:陈东伟  scoreInt:96
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:李宁 82
TokenizerMapper.map...
Map key:105 Map value:李宁 82
name:李宁  scoreInt:82
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:杨森 85
TokenizerMapper.map...
Map key:115 Map value:杨森 85
name:杨森  scoreInt:85
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:陈东奇 72
TokenizerMapper.map...
Map key:125 Map value:陈东奇 72
name:陈东奇  scoreInt:72
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:谭果 97
TokenizerMapper.map...
Map key:138 Map value:谭果 97
name:谭果  scoreInt:97
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:盖盖 82
TokenizerMapper.map...
Map key:148 Map value:盖盖 82
name:盖盖  scoreInt:82
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:陈洲立 46
TokenizerMapper.map...
Map key:158 Map value:陈洲立 46
name:陈洲立  scoreInt:46
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:陈东伟 48
TokenizerMapper.map...
Map key:171 Map value:陈东伟 48
name:陈东伟  scoreInt:48
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:李宁 67
TokenizerMapper.map...
Map key:184 Map value:李宁 67
name:李宁  scoreInt:67
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:杨森 33
TokenizerMapper.map...
Map key:194 Map value:杨森 33
name:杨森  scoreInt:33
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:陈东奇 28
TokenizerMapper.map...
Map key:204 Map value:陈东奇 28
name:陈东奇  scoreInt:28
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:谭果 78
TokenizerMapper.map...
Map key:217 Map value:谭果 78
name:谭果  scoreInt:78
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:盖盖 87
TokenizerMapper.map...
Map key:227 Map value:盖盖 87
name:盖盖  scoreInt:87
context_map:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
line:
TokenizerMapper.map...
Map key:237 Map value:
context_map_111:org.apache.hadoop.mapreduce.Mapper$Context@d4cf771
14/09/20 19:31:16 INFO mapred.MapTask: Starting flush of map output
reducer...
Reducer key:李宁  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@63dbbdf2
score:82
score:87
score:67
key李宁   average:78
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@3d32487
reducer...
Reducer key:杨森  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@63dbbdf2
score:33
score:86
score:85
key杨森   average:68
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@3d32487
reducer...
Reducer key:盖盖  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@63dbbdf2
score:87
score:83
score:82
key盖盖   average:84
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@3d32487
reducer...
Reducer key:谭果  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@63dbbdf2
score:94
score:97
score:78
key谭果   average:89
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@3d32487
reducer...
Reducer key:陈东伟  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@63dbbdf2
score:48
score:90
score:96
key陈东伟   average:78
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@3d32487
reducer...
Reducer key:陈东奇  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@63dbbdf2
score:72
score:78
score:28
key陈东奇   average:59
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@3d32487
reducer...
Reducer key:陈洲立  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@63dbbdf2
score:68
score:67
score:46
key陈洲立   average:60
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@3d32487
14/09/20 19:31:16 INFO mapred.MapTask: Finished spill 0
14/09/20 19:31:16 INFO mapred.Task: Task:attempt_local_0001_m_000000_0 is done. And is in the process of commiting
14/09/20 19:31:17 INFO mapred.JobClient:  map 0% reduce 0%
14/09/20 19:31:19 INFO mapred.LocalJobRunner:
14/09/20 19:31:19 INFO mapred.Task: Task 'attempt_local_0001_m_000000_0' done.
14/09/20 19:31:19 INFO mapred.Task:  Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@5fc24d33
14/09/20 19:31:19 INFO mapred.LocalJobRunner:
14/09/20 19:31:19 INFO mapred.Merger: Merging 1 sorted segments
14/09/20 19:31:19 INFO mapred.Merger: Down to the last merge-pass, with 1 segments left of total size: 102 bytes
14/09/20 19:31:19 INFO mapred.LocalJobRunner:
reducer...
Reducer key:李宁  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@2407325d
score:78
key李宁   average:78
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@52403ee2
reducer...
Reducer key:杨森  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@2407325d
score:68
key杨森   average:68
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@52403ee2
reducer...
Reducer key:盖盖  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@2407325d
score:84
key盖盖   average:84
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@52403ee2
reducer...
Reducer key:谭果  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@2407325d
score:89
key谭果   average:89
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@52403ee2
reducer...
Reducer key:陈东伟  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@2407325d
score:78
key陈东伟   average:78
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@52403ee2
reducer...
Reducer key:陈东奇  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@2407325d
score:59
key陈东奇   average:59
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@52403ee2
reducer...
Reducer key:陈洲立  Reducer values:org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@2407325d
score:60
key陈洲立   average:60
context_reducer:org.apache.hadoop.mapreduce.Reducer$Context@52403ee2
14/09/20 19:31:19 INFO mapred.Task: Task:attempt_local_0001_r_000000_0 is done. And is in the process of commiting
14/09/20 19:31:19 INFO mapred.LocalJobRunner:
14/09/20 19:31:19 INFO mapred.Task: Task attempt_local_0001_r_000000_0 is allowed to commit now
14/09/20 19:31:19 INFO output.FileOutputCommitter: Saved output of task 'attempt_local_0001_r_000000_0' to hdfs://localhost:9000/user/hadoop/score_output
14/09/20 19:31:20 INFO mapred.JobClient:  map 100% reduce 0%
14/09/20 19:31:22 INFO mapred.LocalJobRunner: reduce > reduce
14/09/20 19:31:22 INFO mapred.Task: Task 'attempt_local_0001_r_000000_0' done.
14/09/20 19:31:23 INFO mapred.JobClient:  map 100% reduce 100%
14/09/20 19:31:23 INFO mapred.JobClient: Job complete: job_local_0001
14/09/20 19:31:23 INFO mapred.JobClient: Counters: 22
14/09/20 19:31:23 INFO mapred.JobClient:   Map-Reduce Framework
14/09/20 19:31:23 INFO mapred.JobClient:     Spilled Records=14
14/09/20 19:31:23 INFO mapred.JobClient:     Map output materialized bytes=106
14/09/20 19:31:23 INFO mapred.JobClient:     Reduce input records=7
14/09/20 19:31:23 INFO mapred.JobClient:     Virtual memory (bytes) snapshot=0
14/09/20 19:31:23 INFO mapred.JobClient:     Map input records=22
14/09/20 19:31:23 INFO mapred.JobClient:     SPLIT_RAW_BYTES=116
14/09/20 19:31:23 INFO mapred.JobClient:     Map output bytes=258
14/09/20 19:31:23 INFO mapred.JobClient:     Reduce shuffle bytes=0
14/09/20 19:31:23 INFO mapred.JobClient:     Physical memory (bytes) snapshot=0
14/09/20 19:31:23 INFO mapred.JobClient:     Reduce input groups=7
14/09/20 19:31:23 INFO mapred.JobClient:     Combine output records=7
14/09/20 19:31:23 INFO mapred.JobClient:     Reduce output records=7
14/09/20 19:31:23 INFO mapred.JobClient:     Map output records=21
14/09/20 19:31:23 INFO mapred.JobClient:     Combine input records=21
14/09/20 19:31:23 INFO mapred.JobClient:     CPU time spent (ms)=0
14/09/20 19:31:23 INFO mapred.JobClient:     Total committed heap usage (bytes)=408944640
14/09/20 19:31:23 INFO mapred.JobClient:   File Input Format Counters
14/09/20 19:31:23 INFO mapred.JobClient:     Bytes Read=238
14/09/20 19:31:23 INFO mapred.JobClient:   FileSystemCounters
14/09/20 19:31:23 INFO mapred.JobClient:     HDFS_BYTES_READ=476
14/09/20 19:31:23 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=81132
14/09/20 19:31:23 INFO mapred.JobClient:     FILE_BYTES_READ=448
14/09/20 19:31:23 INFO mapred.JobClient:     HDFS_BYTES_WRITTEN=79
14/09/20 19:31:23 INFO mapred.JobClient:   File Output Format Counters
14/09/20 19:31:23 INFO mapred.JobClient:     Bytes Written=79

5、输出结果：

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