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);
	}
}