// this method creates a list of file extensions that will be searched
    //
    public static ArrayList<String> createAudioExtensionsList()
    {
        ArrayList<String> extensions = new ArrayList<String>();

        extensions.add(".mp3");
        extensions.add(".ogg");
        extensions.add(".flac");
        extensions.add(".wav");
        extensions.add(".3gp");

        return extensions;
    }

    // simple method to get a file extension (does not work with complex extensions like .tar.gz)
    //
    public static String getFileExtension(String fileName)
    {
        String result = fileName.substring(fileName.lastIndexOf("."));
        return result;
    }

    // recursively scans a folder for all files containing one of the file extensions
    //
    public static LinkedList<File> getFilesInFolder(File rootDir, ArrayList<String> extensions)
    {
        LinkedList<File> results = new LinkedList<File>();
        File[] files = rootDir.listFiles();

        for(File file : files)
        {
            if(file.isDirectory())
                results.addAll(getFilesInFolder(file, extensions));
            else
            {
                for(String s : extensions)
                {
                    String ext = getFileExtension(file.getName());
                    if(s.equalsIgnoreCase(ext))
                        results.add(file);
                }
            }
        }
        return results;
    }