public static void concatenate(File[] args, File dest) throws IOException {
    FileChannel in = null, out = null;
    File source;
       long pos = 0;
       long size;
       try {
             out = new FileOutputStream(dest).getChannel();

             for(int i = 0; i < args.length; i++){
                 source = args[i];
            in = new FileInputStream(source).getChannel();

            size = in.size();
            MappedByteBuffer buf = in.map(FileChannel.MapMode.READ_ONLY, pos, size);
            out.write(buf);
            pos+=size;
            in.close();
             }
     } finally {
          if (in != null)      in.close();
          if (out != null)     out.close();
     }

}