如何读取Hadoop中压缩的文件

package org.dba.util;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.CompressionCodecFactory;
import org.apache.hadoop.io.compress.CompressionInputStream;

public class ReadHdfs {
public static void ReadFile(String fileName) throws IOException{
Configuration conf = new Configuration();
Path file = new Path(fileName);
FileSystem fs = FileSystem.get(conf);
FSDataInputStream hdfsInstream = fs.open(file);
CompressionCodecFactory factory = new CompressionCodecFactory(conf);
CompressionCodec codec = factory.getCodec(file);
BufferedReader reader = null;
try{
if(codec == null){
reader = new BufferedReader(new InputStreamReader(hdfsInstream));
}else{
CompressionInputStream comInStream = codec.createInputStream(hdfsInstream);
reader = new BufferedReader(new InputStreamReader(comInStream));
System.out.println(reader.readLine().substring(0, 100));
}
}catch(Exception e){
e.printStackTrace();
}
}
public static void main(String[] args) throws IOException{
ReadFile(args[0]);
}

}