How to create the right path depending from Os

Question

Hi all,
I should do a simple thing
1. Get a dir by a filechooser
2. Get a dir by another filechooser
3. Extract all files' name by 1.
4. Append every filename from 3. to 2.
5. 4.toString()
I have problem in 4. Becouse if I append them as Strings I've to add a separator character between dir an filename. This char id \ under Windows and / under linux. Is here any way to concatate a filename and a dir indipendently from filesystem?
This is the current version that work only on Windows:
            final JFileChooser fc = new JFileChooser();
            fc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
            fc.setDialogTitle("Select Source Folder");
            returnVal = fc.showOpenDialog(this);
            File file = fc.getSelectedFile();
            final JFileChooser fc2 = new JFileChooser();
            fc2.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
            fc2.setDialogTitle("Select Destination Folder");
            returnVal2 = fc2.showOpenDialog(this);
            File file2 = fc2.getSelectedFile();
            if (returnVal2 == JFileChooser.APPROVE_OPTION &&
                returnVal == JFileChooser.APPROVE_OPTION) {
                File allFiles[] = file.listFiles();
                for (int i = 0; i < allFiles.length; i++) {
                    if (allFiles.isFile()) {
Mp3s mp3file = new Mp3s(allFiles[i].getAbsolutePath().
toString(),
file2.getAbsolutePath().
toString() +
"\\" + allFiles[i].getName());
Mp3 is a class that gets 2 strings (1st_path/filename, 2nd_path/filename)
or (1st_path\filename, 2nd_path\filename) depending from OS and that's the dial
Hope everithing is clear.
Tnx in advance
Ciro

Answer 1

The forward slash should be used, regardless of the platform. The only time this may not work under Windows is if you actually pass the string outside of the Java process. But things like:
File x = new File("/some/directory/somefile.ext");
should work under all OS environments. Under Windows, the above will reference whatever the current drive is (C:, for example), so it would resolve to c:\some\directory\somefile.ext when all is said and done. Java takes care of the conversion for you.