要實現或使用地圖降低

Question

我有一個用例，其中從文件文件我一直在使用閱讀奇數行讀奇數記錄的Java地圖縮小：

但作爲每Inputformat類，只讀取「\ n」作爲線路終止。補題想如下：

輸入：
桑帕特
庫馬爾
Hadoop的
mapredue

OUTPUT：
桑帕特
Hadoop的

Answer 1

您可以根據實現所需的輸出你的用這種方式輸入也是:(不需要編寫自定義輸入/輸出格式）

輸入：

sampat1 kumar2 hadoop3 mapredue4 sampat1 kumar2 hadoop3 mapredue4 sampat1 kumar2 hadoop3 mapredue4 sampat1 kumar2 hadoop3 mapredue4 sampat1 kumar2 hadoop3 mapredue4 

輸出：

sampat1 hadoop3 sampat1 hadoop3 sampat1 hadoop3 sampat1 hadoop3 sampat1 hadoop3 

代碼：

import java.io.IOException; 

import org.apache.hadoop.conf.Configuration; 
import org.apache.hadoop.fs.FileSystem; 
import org.apache.hadoop.fs.Path; 
import org.apache.hadoop.io.Text; 
import org.apache.hadoop.mapreduce.Job; 
import org.apache.hadoop.mapreduce.Mapper; 
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; 
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; 


public class OddLine { 

    public static class OddLineMapper extends Mapper<Object, Text, Text, Text> { 

     private StringBuilder sb = new StringBuilder(""); 

     @Override 
     public void map(Object key, Text value, Context context) throws IOException, InterruptedException { 

      String[] lines = value.toString().split(" "); 

      for(int i=0; i < lines.length; i+=2) 
       sb.append(lines[i] + " "); 

      context.write(new Text(""), new Text(sb.toString())); 
     } 
    } 

    public static void main(String[] args) throws Exception { 

     Configuration conf = new Configuration(); 

     Job job = Job.getInstance(conf, "Get odd words"); 
     job.setJarByClass(OddLine.class); 
     job.setMapperClass(OddLineMapper.class); 

     job.setMapOutputKeyClass(Text.class); 
     job.setMapOutputValueClass(Text.class); 
     job.setOutputKeyClass(Text.class); 
     job.setOutputValueClass(Text.class); 

     FileInputFormat.addInputPath(job, new Path(args[0])); 
     FileOutputFormat.setOutputPath(job, new Path(args[1])); 
     FileSystem fs = null; 
     Path dstFilePath = new Path(args[1]); 
     try { 
      fs = dstFilePath.getFileSystem(conf); 
      if (fs.exists(dstFilePath)) 
       fs.delete(dstFilePath, true); 
     } catch (IOException e1) { 
      e1.printStackTrace(); 
     } 
     System.exit(job.waitForCompletion(true) ? 0 : 1); 
    } 
}