zip files portability on win and mac

Hi,

I'm currently developing an application which, among other things,
should zip some folders with all their content (therefore, also
subfolders).
Browsing I found and slightly adapted the following code:

public class ZipUtil {
   private ZipOutputStream cpZipOutputStream = null;
   private String strSource = "";
   private String strTarget = "";
   private String strSubstring = "";

   public void ZipDirectory (String dir2zip, String destFile){
      strSource = dir2zip;
      strTarget = destFile;
      zip();
   }

   private void zip(){
      try{
         File cpFile = new File (strSource);
     if (!cpFile.isFile() && !cpFile.isDirectory() ) {
            System.out.println("\nSource file/directory Not Found!");
            return;
         }
         if (cpFile.isDirectory()) {
            strSubstring = strSource;
         } else {
            strSubstring = "";
         }
     FileOutputStream fos = new FileOutputStream(strTarget);
         cpZipOutputStream = new ZipOutputStream(fos);
         cpZipOutputStream.setLevel(9);
         zipFiles(cpFile);
         cpZipOutputStream.finish();
         cpZipOutputStream.close();
         fos.close();
      }catch (Exception e){
         e.printStackTrace();
      }
   }

   private void zipFiles(File cpFile) {
      if (cpFile.isDirectory()) {
         File [] fList = cpFile.listFiles() ;
         for (int i=0; i< fList.length; i++){
            zipFiles(fList[i]) ;
         }
      } else {
         try {
            String strAbsPath = cpFile.getAbsolutePath();
            String strZipEntryName ="";
            if (!strSubstring.equals("") ){

                  strZipEntryName = strAbsPath.substring(
                  strSource.length()+1, strAbsPath.length());

            } else {
               strZipEntryName = cpFile.getName();
            }
            byte[] b = new byte[ (int)(cpFile.length()) ];
            FileInputStream cpFileInputStream =
               new FileInputStream (cpFile) ;
            cpFileInputStream.read(b, 0, (int)cpFile.length());
            ZipEntry cpZipEntry = new ZipEntry(strZipEntryName);
            cpZipOutputStream.putNextEntry(cpZipEntry );
            cpZipOutputStream.write(b, 0, (int)cpFile.length());
            cpZipOutputStream.closeEntry() ;
            cpFileInputStream.close();
         } catch (Exception e) {
            e.printStackTrace();
         }
      }
   }
}

The problem is that when I run this on Windows, the following line:

strZipEntryName = strAbsPath.substring(strSource.length()+1,
strAbsPath.length());

uses the backslash as File.separator. So the zip file contains all the
folders and subfolders when I extract the zip file on Windows.
On the other hand, if I try to extract on a Mac, it will consider the
backslash as part of the filename.

e.g.
folder\foo.bar

On Windows it's a folder with a foo.bar file inside.
On Mac, it is a file named "folder\foo".

Am I wrong somewhere, or is there any workaround for this problem?
I'd like my zip files to be as portable as my application :)

Thanks in advance for your answer!

gianpi