In previous article, you learn about how to compress a file into a GZip format. In this article, you will learn how to unzip it / decompress the compressed file from a Gzip file.

Gzip example

In this example, it will decompress the Gzip file “/home/mkyong/file1.gz” back to “/home/mkyong/file1.txt“.

package com.mkyong.gzip;
 
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.zip.GZIPInputStream;
 
public class GZipFile
{
    private static final String INPUT_GZIP_FILE = "/home/mkyong/file1.gz";
    private static final String OUTPUT_FILE = "/home/mkyong/file1.txt";
 
    public static void main( String[] args )
    {
    	GZipFile gZip = new GZipFile();
    	gZip.gunzipIt();
    }
 
    /**
     * GunZip it
     */
    public void gunzipIt(){
 
     byte[] buffer = new byte[1024];
 
     try{
 
    	 GZIPInputStream gzis = 
    		new GZIPInputStream(new FileInputStream(INPUT_GZIP_FILE));
 
    	 FileOutputStream out = 
            new FileOutputStream(OUTPUT_FILE);
 
        int len;
        while ((len = gzis.read(buffer)) > 0) {
        	out.write(buffer, 0, len);
        }
 
        gzis.close();
    	out.close();
 
    	System.out.println("Done");
 
    }catch(IOException ex){
       ex.printStackTrace();   
    }
   } 
}

Reference

  1. http://java.sun.com/developer/technicalArticles/Programming/compression/
  2. http://www.gzip.org/
  3. http://en.wikipedia.org/wiki/Gzip
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