Hadoop MapReduce排序程式_Hadoop

    package com.hadoop.sample;            import java.io.IOException;      import java.util.StringTokenizer;            import org.apache.hadoop.conf.Configuration;      import org.apache.hadoop.fs.Path;      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.output.FileOutputFormat;      import org.apache.hadoop.util.GenericOptionsParser;            public class Sort {          //map將輸入中的value化成IntWritable類型，作為輸出的key          public static class Map extends Mapper<Object,Text,IntWritable,IntWritable>{              private static IntWritable data = new IntWritable();              public void map(Object key,Text value,Context context) throws IOException,InterruptedException{                   String line = value.toString();                   data.set(Integer.parseInt(line));                   context.write(data, new IntWritable(1));              }          }          //reduce將輸入中的key複製到輸出的value上，然後根據輸入的          //value-list中的元素的個數決定key的輸出次數          //用全域的linenum來代表key的位次          public static class Reduce extends Reducer<IntWritable,IntWritable,IntWritable,IntWritable>{              private static IntWritable linenum = new IntWritable(1);              public void reduce(IntWritable key,Iterable<IntWritable> values,Context context) throws IOException,InterruptedException{                  for(IntWritable val:values){                      context.write(linenum, key);                      linenum = new IntWritable(linenum.get()+1);                  }                                }          }          /**          * @param args          */          public static void main(String[] args) throws Exception{              // TODO Auto-generated method stub              Configuration conf = new Configuration();              String[] otherArgs = new GenericOptionsParser(conf,args).getRemainingArgs();              if(otherArgs.length != 2){                  System.err.println("Usage WordCount <int> <out>");                  System.exit(2);              }              Job job = new Job(conf,"Sort");              job.setJarByClass(Sort.class);              job.setMapperClass(Map.class);              job.setCombinerClass(Reduce.class);              job.setReducerClass(Reduce.class);              job.setOutputKeyClass(IntWritable.class);              job.setOutputValueClass(IntWritable.class);              FileInputFormat.addInputPath(job, new Path(otherArgs[0]));              FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));              System.exit(job.waitForCompletion(true) ? 0 : 1);          }            }