我一直在试图运行这个项目，我发现在互联网上，为我的意图改变。
map函数被调用并正常工作，我从控制台检查了结果。但是reduce没有被调用
前两位是键，其余是值。

我已经控制了Map输出和reduce输入键、值对之间的匹配，我已经多次更改它们，尝试了不同的方法，但都没有找到解决方案。
因为我是这个主题的初学者，可能有一个小错误。我写了另一个项目，又犯了同样的错误“reduce is not called”
我还尝试将reduce的output valu类更改为intwritable、textwritable而不是medianstdevtuple，并配置了作业，但没有任何更改。
我不需要唯一的解决办法，我也想知道原因。谢谢。这是密码

package usercommend;

import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;

import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
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.Mapper.Context;
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;
import org.apache.htrace.commons.logging.LogFactory;

import usercommend.starter.map;

public class starter extends Configured implements Tool {

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

    @Override
    public int run(String[] args) throws Exception {
        Job job=Job.getInstance(getConf(),"starter");
        job.setJarByClass(this.getClass());

        job.setMapperClass(map.class);
        job.setReducerClass(reduces.class);
        job.setMapOutputKeyClass(IntWritable.class);
        job.setMapOutputValueClass(IntWritable.class);

        job.setOutputKeyClass(IntWritable.class);
        job.setOutputValueClass(MedianStdDevTuple.class);

        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        return job.waitForCompletion(true) ? 0 : 1;

    }

    public static class map extends Mapper<LongWritable, Text,IntWritable, IntWritable> {
        private IntWritable outHour = new IntWritable();
        private IntWritable outCommentLength = new IntWritable();
        private final static SimpleDateFormat frmt = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS");

        @SuppressWarnings("deprecation")
        @Override
        public void map(LongWritable key , Text value,Context context) throws IOException, InterruptedException
        {
            //System.err.println(value.toString()+"vv");
            Map<String, String> parsed = transforXmlToMap1(value.toString());
            //System.err.println("1");
            String strDate = parsed.get("CreationDate");
            //System.err.println(strDate);
            String text = parsed.get("Text");
            //System.err.println(text);
            Date creationDate=new Date();
            try {
            //  System.err.println("basla");
                 creationDate = frmt.parse(strDate);
                    outHour.set(creationDate.getHours());
                    outCommentLength.set(text.length());
                    System.err.println(outHour+""+outCommentLength);
                    context.write(outHour, outCommentLength);
            } catch (ParseException e) {
                // TODO Auto-generated catch block
                System.err.println("catch");
                e.printStackTrace();
                return;
            }

            //context.write(new IntWritable(2), new IntWritable(12));
        }

        public static Map<String,String> transforXmlToMap1(String xml) {

            Map<String, String> map = new HashMap<String, String>();
            try {
                String[] tokens = xml.trim().substring(5, xml.trim().length()-3).split("\"");

                for(int i = 0; i < tokens.length-1 ; i+=2) {
                    String key = tokens[i].trim();
                    String val = tokens[i+1];

                    map.put(key.substring(0, key.length()-1),val);
                    //System.err.println(val.toString());
                }
            } catch (StringIndexOutOfBoundsException e) {
                System.err.println(xml);
            }
            return map;
        }
    }

    public static class reduces extends Reducer<IntWritable, IntWritable, IntWritable, MedianStdDevTuple> {

        private MedianStdDevTuple result = new MedianStdDevTuple();
        private ArrayList<Float> commentLengths = new ArrayList<Float>();
        Log log=(Log) LogFactory.getLog(this.getClass());

        @Override
        public void reduce(IntWritable key, Iterable<IntWritable> values,Context context) throws IOException, InterruptedException{
            System.out.println("1");
            log.info("aa");
            float sum = 0;
            float count = 0;
            commentLengths.clear();
            result.setStdDev(0);

            for(IntWritable val : values) {
                commentLengths.add((float)val.get());
                sum+=val.get();
                ++count;        
            }

            Collections.sort(commentLengths);

            if(count % 2 ==0) {
                result.setMedian((commentLengths.get((int)count / 2 -1)+
                            commentLengths.get((int) count / 2)) / 2.0f);
            } else {
                result.setMedian(commentLengths.get((int)count / 2));
            }

            double avg = sum/commentLengths.size();
            double totalSquare = 0;
            for(int i =0 ;i<commentLengths.size();i++) {
                double diff = commentLengths.get(i)-avg;
                totalSquare += (diff*diff);
            }

            double stdSapma= Math.sqrt(totalSquare/(commentLengths.size()));
            result.setStdDev(stdSapma);
            context.write(key, result);
        }
    }
}

样本输入

<row Id="2" PostId="7" Score="0" Text="I see what you mean, but I've had Linux systems set up so that if the mouse stayed on a window for a certain time period (greater than zero), then that window became active.  That would be one solution.  Another would be to simply let clicks pass to whatever control they are over, whether it is in the currently active window or not.  Is that doable?" CreationDate="2010-08-17T19:38:20.410" UserId="115" />
<row Id="3" PostId="13" Score="1" Text="I am using Iwork and OpenOffice right now But I need some features that just MS has it." CreationDate="2010-08-17T19:42:04.487" UserId="135" />
<row Id="4" PostId="17" Score="0" Text="I've been using that on my MacBook Pro since I got it, with no issues.  Last week I got an iMac and immediately installed StartSound.PrefPane but it doesn't work -- any ideas why?  The settings on the two machines are identical (except the iMac has v1.1b3 instead of v1.1b2), but one is silent at startup and the other isn't...." CreationDate="2010-08-17T19:42:15.097" UserId="115" />
<row Id="5" PostId="6" Score="0" Text="+agreed.  I would add that I think you can choose to not clone everything so it takes less time to make a bootable volume" CreationDate="2010-08-17T19:44:00.270" UserId="2" />
<row Id="6" PostId="22" Score="2" Text="Applications are removed from memory by the OS at it's discretion.  Just because they are in the 'task manager' does not imply they are running and in memory.  I have confirmed this with my own apps.&#xA;&#xA;After a reboot, these applications are not reloaded until launched by a user." CreationDate="2010-08-17T19:46:01.950" UserId="589" />
<row Id="7" PostId="7" Score="0" Text="Honestly, I don't know.  It's definitely interesting though.  I'm currently scouring Google, since it would save on input clicks.  I'm just concerned that any solution might get a little &quot;hack-y&quot; and not behave consistently in all UI elements or applications.  The last thing I'd want is to not know if I'm focusing a window or pressing a button :(" CreationDate="2010-08-17T19:50:00.723" UserId="421" />
<row Id="8" PostId="21" Score="3" Text="Could you expand on the features for those not familiar with ShakesPeer?" CreationDate="2010-08-17T19:51:11.953" UserId="581" />
<row Id="9" PostId="23" Score="1" Text="Apple's vernacular is Safe Sleep." CreationDate="2010-08-17T19:51:35.557" UserId="171" />