How to Compress a File in GZIP Format

The below code would compress a specified file to GZip format. In the below example we have a text file in B drive under “Java” Folder and we are compressing and generating the GZip file in the same folder.

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.zip.GZIPOutputStream;
 
public class GZipExample
{
  public static void main( String[] args )
  {
    GZipExample zipObj = new GZipExample();
    zipObj.gzipMyFile();
  }
 
  public void gzipMyFile(){ 
    byte[] buffer = new byte[1024];
    try{
      //Specify Name and Path of Output GZip file here
      GZIPOutputStream gos = 
       new GZIPOutputStream(new FileOutputStream("B://Java/Myfile.gz"));
 
      //Specify location of Input file here
      FileInputStream fis = 
       new FileInputStream("B://Java/Myfile.txt");
 
      //Reading from input file and writing to output GZip file
      int length;
      while ((length = fis.read(buffer)) > 0) {
 
        /* public void write(byte[] buf, int off, int len): 
         * Writes array of bytes to the compressed output stream.
         * This method will block until all the bytes are written.
         * Parameters:
         * buf - the data to be written
         * off - the start offset of the data
         * len - the length of the data
         */
        gos.write(buffer, 0, length);
      }
 
      fis.close();
 
      /* public void finish(): Finishes writing compressed 
       * data to the output stream without closing the 
       * underlying stream.
       */
      gos.finish();
      gos.close();
 
      System.out.println("File Compressed!!");
 
    }catch(IOException ioe){
        ioe.printStackTrace(); 
     }
  }
}

Output:

File Compressed!!

Reference:
GZIPOutputStream javadoc