// Tutorial //

Java GZIP Example - Compress and Decompress File

Published on August 3, 2022
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By Pankaj
Developer and author at DigitalOcean.
Java GZIP Example - Compress and Decompress File

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Welcome to Java GZIP example. GZIP is one of the favorite tool to compress file in Unix systems. We can compress a single file in GZIP format but we can’t compress and archive a directory using GZIP like ZIP files.

Java GZIP

GZIP, Java GZIP Example Here is a simple java GZIP example program showing how can we compress a file to GZIP format and then decompress the GZIP file to create a new file. GZIPExample.java

package com.journaldev.files;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

public class GZIPExample {

    public static void main(String[] args) {
        String file = "/Users/pankaj/sitemap.xml";
        String gzipFile = "/Users/pankaj/sitemap.xml.gz";
        String newFile = "/Users/pankaj/new_sitemap.xml";
        
        compressGzipFile(file, gzipFile);
        
        decompressGzipFile(gzipFile, newFile);
               
    }

    private static void decompressGzipFile(String gzipFile, String newFile) {
        try {
            FileInputStream fis = new FileInputStream(gzipFile);
            GZIPInputStream gis = new GZIPInputStream(fis);
            FileOutputStream fos = new FileOutputStream(newFile);
            byte[] buffer = new byte[1024];
            int len;
            while((len = gis.read(buffer)) != -1){
                fos.write(buffer, 0, len);
            }
            //close resources
            fos.close();
            gis.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        
    }

    private static void compressGzipFile(String file, String gzipFile) {
        try {
            FileInputStream fis = new FileInputStream(file);
            FileOutputStream fos = new FileOutputStream(gzipFile);
            GZIPOutputStream gzipOS = new GZIPOutputStream(fos);
            byte[] buffer = new byte[1024];
            int len;
            while((len=fis.read(buffer)) != -1){
                gzipOS.write(buffer, 0, len);
            }
            //close resources
            gzipOS.close();
            fos.close();
            fis.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        
    }

}

While decompressing a GZIP file, if it’s not in GZIP format, following exception will be thrown.

java.util.zip.ZipException: Not in GZIP format
	at java.util.zip.GZIPInputStream.readHeader(GZIPInputStream.java:164)
	at java.util.zip.GZIPInputStream.<init>(GZIPInputStream.java:78)
	at java.util.zip.GZIPInputStream.<init>(GZIPInputStream.java:90)
	at com.journaldev.files.GZIPExample.decompressGzipFile(GZIPExample.java:25)
	at com.journaldev.files.GZIPExample.main(GZIPExample.java:18)

That’s all for Java GZIP Example.

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About the authors
Default avatar
Pankaj

author

Developer and author at DigitalOcean.

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JournalDev
DigitalOcean Employee
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February 7, 2018

Excellent example. Thanks for sharing.

- Mayur Musrif

    JournalDev
    DigitalOcean Employee
    DigitalOcean Employee badge
    July 14, 2016

    Hi When compressing the file, before you gzipOS.close() run gzipOS.finish(). It should help.

    - Tomek

      JournalDev
      DigitalOcean Employee
      DigitalOcean Employee badge
      October 31, 2014

      Hey can u please mail me the explanation of this program… step wise…

      - Rituraj Dharwadkar

        JournalDev
        DigitalOcean Employee
        DigitalOcean Employee badge
        June 17, 2014

        This post is very helpful. Could you please make a sample gzip xml file available for download. Plus, is there an easy way to generate a gzip json file? Thanks,

        - longlife

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