MapReduce求最大值最小值问题

import java.io.File;
import java.io.IOException;
 
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.JobConf;
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 GetMinMaxKeyMapReduce {
     
    public static class GetMinMaxKeyMap extends Mapper<Object, Text, Text,Text> {
        private Text min = new Text();
        private Text max = new Text();
        private Long i = new Long(0);
        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
            String[] strs = value.toString().split("\t");
            if (strs!=null && strs.length>5 &&strs[3].length() > 20 && strs[3].indexOf(" ") == -1 && strs[3].indexOf("=") == -1) {
                if(i==0){
                    min= new Text(strs[3]);
                    max= new Text(strs[3]);
                }
                if(strs[3].compareTo(min.toString())<0){
                    min=new Text(strs[3]);
                }
                if(strs[3].compareTo(max.toString())>0){
                    max=new Text(strs[3]);
                }
                i++;
            }
        }
         
        @Override
        protected void cleanup(Context context) throws IOException, InterruptedException {
            context.write(new Text("min"), min);
            context.write(new Text("max"), max);
        }
    }
 
    public static class GetMinMaxKeyReducer extends Reducer<Text, Text, Text, Text> {
        public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
            String result ="";
            for (Text value : values) {
                if(result.equals("")){
                    result = value.toString();
                }
                if (("min").equals(key.toString())) {
                    if(value.toString().compareTo(result)<0){
                        result=value.toString();
                    }
                } else if (("max").equals(key.toString())) {
                    if(value.toString().compareTo(result)>0){
                        result=value.toString();
                    }
                } else {
                    System.err.println("未知reduce 输入key:" + key.toString());
                }
            }
            context.write(key, new Text(result));
        }
    }
 
    public static void main(String[] args) throws Exception {
        File jarFile = EJob.createTempJar("bin");
        ClassLoader classLoader = EJob.getClassLoader();
        Thread.currentThread().setContextClassLoader(classLoader);
         
        //Hadoop 运行环境
        Configuration conf = new Configuration();
        conf.set("mapred.job.tracker", "bfdbjc1:12001");;
         
        //任务参数设置
        Job job = new Job(conf, "GetMinMaxKey");
 
        job.setJarByClass(GetMinMaxKeyMapReduce.class);
        job.setMapperClass(GetMinMaxKeyMap.class);
        job.setReducerClass(GetMinMaxKeyReducer.class);
 
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(Text.class);
 
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);
         
        FileInputFormat.addInputPath(job, new Path("hdfs://bfdbjc1:12000/user/work/tables2/raw_kafka/l_date=2013-09-15"));
        FileOutputFormat.setOutputPath(job, new Path("hdfs://bfdbjc1:12000/user/work/output/minmaxkey/"));
         
        //Eclipse 本地提交
        ((JobConf) job.getConfiguration()).setJar(jarFile.toString());
         
        //等待任务运行完成
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}