请教MapReduce难题！

最近开始研究Mapreduce了，但是发现里面所有的examples都是用旧的API写的，现在想将其用新的API重写，重写后代码如下，但是总出现错误，还请教高手指点。
[ol]

package cn.edu.neu.mapreduce;

import java.io.IOException;

import java.util.Random;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.conf.Configured;

import org.apache.hadoop.fs.FileSystem;

import org.apache.hadoop.fs.Path;

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.lib.input.FileInputFormat;

import org.apache.hadoop.mapreduce.lib.input.SequenceFileInputFormat;

import org.apache.hadoop.mapreduce.lib.map.InverseMapper;

import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;

import org.apache.hadoop.mapreduce.lib.reduce.LongSumReducer;

import org.apache.hadoop.util.GenericOptionsParser;

import org.apache.hadoop.util.Tool;

import org.apache.hadoop.util.ToolRunner;

public class Grep extends Configured implements Tool {

private Grep() {

}

@Override

public int run(String[] args) throws Exception {

// TODO Auto-generated method stub

if (args.length []");

ToolRunner.printGenericCommandUsage(System.out);

return -1;

}

Path tempDir = new Path("grep-temp-"

+ Integer.toString(new Random().nextInt(Integer.MAX_VALUE)));

String[] otherArgs = new GenericOptionsParser(getConf(), args)

.getRemainingArgs();

Job job = new Job(getConf(), "Grep");

try {

job.setJobName("grep-search");

job.setJarByClass(Grep.class);

FileInputFormat.setInputPaths(job, otherArgs[0]);

job.setMapperClass(RegexMapper.class);

job.getConfiguration().set("mapred.mapper.regex", otherArgs[2]);

if (otherArgs.length == 4)

job.getConfiguration().set("mapred.mapper.regex.group",

otherArgs[3]);

job.setCombinerClass(LongSumReducer.class);

job.setReducerClass(LongSumReducer.class);

FileOutputFormat.setOutputPath(job, tempDir);

job.setOutputFormatClass(SequenceFileOutputFormat.class);

job.setOutputKeyClass(Text.class);

job.setOutputValueClass(LongWritable.class);

job.waitForCompletion(true);

Job sortJob = new Job(getConf(), "Sort");

sortJob.setJobName("grep-sort");

FileInputFormat.setInputPaths(sortJob, tempDir);

sortJob.setInputFormatClass(SequenceFileInputFormat.class);

sortJob.setMapperClass(InverseMapper.class);

sortJob.setNumReduceTasks(1);

FileOutputFormat.setOutputPath(sortJob, new Path(otherArgs[1]));

sortJob.setOutputKeyClass(LongWritable.DecreasingComparator.class);

job.waitForCompletion(true);

} finally {

FileSystem.get(job.getConfiguration()).delete(tempDir, true);

}

return 0;

}

/**

* @param args

*/

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

// TODO Auto-generated method stub

int res = ToolRunner.run(new Configuration(), new Grep(), args);

System.exit(res);

}

public class RegexMapper extends Mapper {

private Pattern pattern;

private int group;

public void map(K key, Text value, Context context) throws IOException,

InterruptedException {

pattern = Pattern.compile(context.getConfiguration().get(

"mapred.mapper.regex"));

group = context.getConfiguration().getInt(

"mapred.mapper.regex.group", 0);

String text = value.toString();

Matcher matcher = pattern.matcher(text);

while (matcher.find()) {

try {

context.write(new Text(matcher.group(group)),

new LongWritable(1));

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}[/ol]复制代码
错误提示：
09/12/24 15:26:50 INFO input.FileInputFormat: Total input paths to process : 1
09/12/24 15:26:51 INFO mapred.JobClient: Running job: job_200912241430_0008
09/12/24 15:26:52 INFO mapred.JobClient: map 0% reduce 0%
09/12/24 15:27:02 INFO mapred.JobClient: Task Id : attempt_200912241430_0008_m_000000_0, Status : FAILED
java.lang.RuntimeException: java.lang.NoSuchMethodException: cn.edu.neu.mapreduce.Grep$RegexMapper.()
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:532)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:305)
at org.apache.hadoop.mapred.Child.main(Child.java:170)
Caused by: java.lang.NoSuchMethodException: cn.edu.neu.mapreduce.Grep$RegexMapper.()
at java.lang.Class.getConstructor0(Class.java:2706)
at java.lang.Class.getDeclaredConstructor(Class.java:1985)
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:109)
... 3 more