write & read a MapFile（基于全新2.2.0API）

write & read a  MapFile

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 import java.io.IOException;
 
 import org.apache.hadoop.io.IntWritable;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.io.MapFile;
 import org.apache.hadoop.io.MapFile.Writer;
 import org.apache.hadoop.io.MapFile.Reader;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 
 public class MyMapFile {
 
   static private final String[] DATA =  {
       "this is the first",
       "this is the second",
       "this is the third",
       "this is the forth"
     };  
 
   public static void main(String[] args) throws IOException {
     Configuration conf = new Configuration();
     FileSystem fs = FileSystem.get(conf);
     String uri = args[0];
 
     IntWritable key = new IntWritable();
     Text val = new Text();
 
     MapFile.Writer writer = new MapFile.Writer(conf, new Path(uri), Writer.keyClass(key.getClass()), Writer.valueClass(val.getClass())); 
 
     for( int i = 0; i < 10; i++ ) {
       key.set( i + 1 );
       val.set(DATA[ i % DATA.length ]);
       writer.append(key, val);
     }
     writer.close();
 
     MapFile.Reader reader = new MapFile.Reader(new Path(uri), conf);
 
     while( reader.next(key, val) ){
       System.out.println( key + "\t" + val );
     }
     reader.close();
   }
 }