docs: public static void copyFile(File in, File out) throws IOException {
       FileChannel inChannel = new
           FileInputStream(in).getChannel();
       FileChannel outChannel = new
           FileOutputStream(out).getChannel();
       try {
           inChannel.transferTo(0, inChannel.size(), outChannel);
       } 
       catch (IOException e) {
           throw e;
       }
       finally {
           if (inChannel != null)  { 
               inChannel.close();
           }
           if (outChannel != null)  {
               outChannel.close();
           }
       }
   }