Compress And Decompress File Using GZIP Format in Java

In this post we'll see how to use GZIP to compress and decompress a file in Java. You will mainly use GZIP tool to compress and decompress files in Unix systems. Here note that you can only compress a single file using GZIP not multiple files residing in a folder.

Refer Creating Tar File And GZipping Multiple Files - Java Program to see how to gzip multiple files in Java.

Steps to gzip a file

In order to compress a file using GZIP in Java the steps are as follows-

For reading the source file (file which has to be GZIPped) create a FileInputStream.
Create a FileOutputStream to the target file (output GZIPped file).
Create a GZIPOutputStream wrapping the FileOutputStream.
Then you just need to read from the input stream and write to the output stream.

Steps to decompress a file

In order to decompress a file using GZIP in Java the steps are as follows-

For reading the compressed file create a FileInputStream.
Wrap that FileInputStream with in a GZIPInputStream.
Create a FileOutputStream to the new file (created on decompressing GZIP file).
Then you just need to read from the input stream and write to the output stream.

Java example for compressing and decompressing file in GZIP format

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

public class GZipDemo {

 public static void main(String[] args) {
  // Path to file which is gzipped
  String SOURCE_FILE = "G:\\Test\\abc.txt";
  // Path to gzipped output files
  String GZIP_OUTPUT_FILE = "G:\\Test\\abc.gz";
  // File you get after decompressings
  String GZIP_NEW_FILE = "G:\\Test\\newabc.txt";
  
  GZipDemo gZipDemo = new GZipDemo();
  try {
   // Compressing a file
   gZipDemo.compressGZipFile(SOURCE_FILE, GZIP_OUTPUT_FILE);
   
   // decompressing a file
   gZipDemo.deCompressGZipFile(GZIP_OUTPUT_FILE, GZIP_NEW_FILE);
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

 }
 /**
  * Method to gzip a file
  * @param sourceFile
  * @param outputFile
  * @throws IOException
  */
 public void compressGZipFile(String sourceFile, String outputFile) 
    throws IOException{
  FileInputStream fis = new FileInputStream(sourceFile);
  FileOutputStream fos = new FileOutputStream(outputFile);
  GZIPOutputStream gZIPOutputStream = new GZIPOutputStream(fos); 
  byte[] buffer = new byte[1024];
  int len;
  while((len = fis.read(buffer)) > 0){
   gZIPOutputStream.write(buffer, 0, len);
  }
  // Keep it in finally
  fis.close();
  gZIPOutputStream.close();
 }
 
 /**
  * Method to decompress a gzip file
  * @param gZippedFile
  * @param newFile
  * @throws IOException
  */
 public void deCompressGZipFile(String gZippedFile, String newFile) 
    throws IOException{
  FileInputStream fis = new FileInputStream(gZippedFile);
  GZIPInputStream gZIPInputStream = new GZIPInputStream(fis);
  FileOutputStream fos = new FileOutputStream(newFile);
  byte[] buffer = new byte[1024];
  int len;
  while((len = gZIPInputStream.read(buffer)) > 0){
   fos.write(buffer, 0, len);
  }
  // Keep it in finally
  fos.close();
  gZIPInputStream.close();
 }
}

That's all for this topic Compress And Decompress File Using GZIP Format in Java. If you have any doubt or any suggestions to make please drop a comment. Thanks!

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Sunday, April 24, 2022