public void zipFiles(){
    FileOutputStream fos = null;
    ZipOutputStream zipOut = null;
    FileInputStream fis = null;
    try {
        File folder = new File("D:\Data\attachment");
        File[] attachFiles = folder.listFiles();

        fos = new FileOutputStream("C:\Users\admin\Desktop\tai-lieu\testing.zip");
        zipOut = new ZipOutputStream(new BufferedOutputStream(fos));
        for(File file: attachFiles){
            fis = new FileInputStream(file);
            ZipEntry ze = new ZipEntry(file.getName());
            System.out.println("Zipping the file: "+file.getName());
            zipOut.putNextEntry(ze);
            byte[] tmp = new byte[1024];
            int size = 0;
            while((size = fis.read(tmp)) != -1){
                zipOut.write(tmp, 0, size);
            }
            zipOut.flush();
            fis.close();
        }
        zipOut.close();
        System.out.println("Done... Zipped the files...");
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } finally{
        try{
            if(fos != null) fos.close();
        } catch(Exception ex){

        }
    }
}