任务描述：

一组数据，按照年份的不同将其分别存放在不同的文件里

example Data：

2013 1
2013 5
2014 5
2014 8
2015 9
2015 4

Code：

package mrTest;import java.io.IOException;
import java.util.StringTokenizer;import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
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.Partitioner;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;public class zidingyiPartition {public static class myPartition extends Partitioner<LongWritable, LongWritable>{public int getPartition(LongWritable key, LongWritable value, int numTaskReduces) {// TODO Auto-generated method stubif(key.get()==2013){return 0;}else if(key.get()==2014){return 1;}else{return 2;}}}public static class Map extends Mapper<Object, Text, LongWritable,LongWritable>{public void map(Object key, Text value, Context context) throws IOException, InterruptedException{String[] line = value.toString().split("\t");context.write( new LongWritable(Integer.parseInt(line[0])) ,  new LongWritable(Integer.parseInt(line[1])) );}}public static class Reduce extends Reducer<LongWritable, LongWritable, LongWritable, LongWritable>{public void reduce(LongWritable key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException{for (LongWritable longWritable : values) {context.write(key, longWritable);}}}public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {// TODO Auto-generated method stubJob job = new Job();job.setJarByClass(zidingyiPartition.class);//  1FileInputFormat.addInputPath(job, new Path(args[0]));// 2job.setMapperClass(Map.class);job.setMapOutputKeyClass(LongWritable.class);job.setMapOutputValueClass(LongWritable.class);//   3job.setPartitionerClass(myPartition.class);//  4//  5job.setNumReduceTasks(3);//  6job.setReducerClass(Reduce.class);job.setOutputKeyClass(LongWritable.class);job.setOutputValueClass(LongWritable.class);//  7FileOutputFormat.setOutputPath(job, new Path(args[1]));//  8System.exit(job.waitForCompletion(true)? 0 : 1);}}

结果展示：