Excel size in Jasper Report

Hi,

I am exporting one jxml file to xls file. while doing so suppose the file size is 1000kb while it is created, but when i further edit that same file and save it the size decreases to 500kb ie half of the former size.

Now can anyone tell me how to solve this issue?
Is there any way to specify the file size before exporting or is there any parameter which is related to size of the file?

Following is the code snippet i am using

[color=olive]/**
     * Export to xls format.
     * 
     * @param parameters the parameters
     * @param jRXMLID the jrxml id
     * @param pdfNameWithExtention the pdf name with extension
     */
    private void exportToXLSFormat(Map parameters, String jRXMLID,
			String pdfNameWithExtension) throws JRException {

int index = pdfNameWithExtension.indexOf(".");

// Destination file name with XLS extension
		String destinationFilename = pdfNameWithExtension.substring(0, index)
				+ ".xls";

// Get the input steam from JASPER object
		InputStream reportInputStream = getClass().getClassLoader()
				.getResourceAsStream(jRXMLID + ".jasper");

// Get the data data source from map
		JRDataSource source = new JRBeanCollectionDataSource(
				(ArrayList) parameters.get("REPORT_DATA_LIST"));

// Setting below attribute to avoid the pagination
		parameters.put("IS_IGNORE_PAGINATION", Boolean.TRUE);
	    parameters.put(JRExporterParameter.OFFSET_X, Boolean.TRUE);

// Get the JASPER Print object
		JasperPrint jasperPrint = JasperFillManager.fillReport(
				reportInputStream, parameters, source);

// XLS Object to export the report in XL format
		JRXlsExporter exporter = new JRXlsExporter();
		exporter.setParameter(JRExporterParameter.OFFSET_X,);
		exporter.setParameter(JRExporterParameter.JASPER_PRINT, jasperPrint);
		exporter.setParameter(JRExporterParameter.OUTPUT_FILE_NAME, "/usr/tmp/"
				+ destinationFilename);
		exporter.exportReport();
}[/color]

Welcome to the Ranch!

What does it matter what size the file has? As long as all the data, formatting and functionality is still present, isn't that all that matters?

I know data, formatting and functionality and other things are coming correectly.
But i want to know why the file size is decreasing. Generally it should not happen.

Some one please help me.