code: public void compress()
          throws ArchiverException
      {
          try
          {
              zOut = new GZIPOutputStream( Streams.bufferedOutputStream( new FileOutputStream( getDestFile() ) ));
              compress( getSource(), zOut );
          }
          catch ( IOException ioe )
          {
              String msg = "Problem creating gzip " + ioe.getMessage();
              throw new ArchiverException( msg, ioe );
          }
      }
docs: perform the GZip compression operation.