MapReduceは大量のデータの中の最大値を求めます

package jtlyuan.csdn;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.IntWritable;
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.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
// 
public class MaxNum extends Configured implements Tool {
public static class MapClass extends Mapper<LongWritable, Text, IntWritable, IntWritable> {
private int maxNum = 0;
public void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
String[] str = value.toString().split(",", 2);
try {//  
int temp = Integer.parseInt(str[0]);
if (temp > maxNum) {
maxNum = temp;
}
} catch (NumberFormatException e) {
}
}
@Override
protected void cleanup(Context context) throws IOException,
InterruptedException {
context.write(new IntWritable(maxNum), new IntWritable(maxNum));
}
}
public static class Reduce extends Reducer<IntWritable, IntWritable, IntWritable, IntWritable> {
private int maxNum = 0;
public void reduce(IntWritable key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
for (IntWritable val : values) {
if ( val.get() > maxNum) {
maxNum = val.get();
}
}
}
@Override
protected void cleanup(Context context) throws IOException,
InterruptedException {
context.write(new IntWritable(maxNum), new IntWritable(maxNum));
}
}
public int run(String[] args) throws Exception {
Configuration conf = getConf();
Job job = new Job(conf, "MaxNum");
job.setJarByClass(MaxNum.class);
FileInputFormat.setInputPaths(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
job.setMapperClass(MapClass.class);
job.setCombinerClass(Reduce.class);
job.setReducerClass(Reduce.class);
job.setInputFormatClass(TextInputFormat.class);
job.setOutputFormatClass(TextOutputFormat.class);
job.setOutputKeyClass(IntWritable.class);
job.setOutputValueClass(IntWritable.class);
System.exit(job.waitForCompletion(true) ? 0 : 1);
return 0;
}
public static void main(String[] args) throws Exception {
long start = System.nanoTime();
int res = ToolRunner.run(new Configuration(), new MaxNum(), args);
System.out.println(System.nanoTime()-start);
System.exit(res);
}
}
/*
*  ：6009554 6009554
*
*/