public static void main(String[] arguments) {
   try {
     // read byte data into a byte buffer
     String data = "friends.dat";
     FileInputStream inData = new FileInputStream(data);
     FileChannel inChannel = inData.getChannel();
     long inSize = inChannel.size();
     ByteBuffer source = ByteBuffer.allocate((int) inSize);
     inChannel.read(source, 0);
     source.position(0);
     System.out.println("Original byte data:");
     for (int i = 0; source.remaining() > 0; i++) {
       System.out.print(source.get() + " ");
     }
     // convert byte data into character data
     source.position(0);
     Charset ascii = Charset.forName("US-ASCII");
     CharsetDecoder toAscii = ascii.newDecoder();
     CharBuffer destination = toAscii.decode(source);
     destination.position(0);
     System.out.println("\n\nNew character data:");
     for (int i = 0; destination.remaining() > 0; i++) {
       System.out.print(destination.get());
     }
     System.out.println();
   } catch (FileNotFoundException fne) {
     System.out.println(fne.getMessage());
   } catch (IOException ioe) {
     System.out.println(ioe.getMessage());
   }
 }
  public static void main(String args[]) throws Exception {
    String inputFile = "samplein.txt";
    String outputFile = "sampleout.txt";

    RandomAccessFile inf = new RandomAccessFile(inputFile, "r");
    RandomAccessFile outf = new RandomAccessFile(outputFile, "rw");
    long inputLength = new File(inputFile).length();

    FileChannel inc = inf.getChannel();
    FileChannel outc = outf.getChannel();

    MappedByteBuffer inputData = inc.map(FileChannel.MapMode.READ_ONLY, 0, inputLength);

    Charset latin1 = Charset.forName("ISO-8859-1");
    CharsetDecoder decoder = latin1.newDecoder();
    CharsetEncoder encoder = latin1.newEncoder();

    CharBuffer cb = decoder.decode(inputData);

    // Process char data here

    ByteBuffer outputData = encoder.encode(cb);

    outc.write(outputData);

    inf.close();
    outf.close();
  }
  /**
   * Decode file charset.
   *
   * @param f File to process.
   * @return File charset.
   * @throws IOException in case of error.
   */
  public static Charset decode(File f) throws IOException {
    SortedMap<String, Charset> charsets = Charset.availableCharsets();

    String[] firstCharsets = {
      Charset.defaultCharset().name(), "US-ASCII", "UTF-8", "UTF-16BE", "UTF-16LE"
    };

    Collection<Charset> orderedCharsets = U.newLinkedHashSet(charsets.size());

    for (String c : firstCharsets)
      if (charsets.containsKey(c)) orderedCharsets.add(charsets.get(c));

    orderedCharsets.addAll(charsets.values());

    try (RandomAccessFile raf = new RandomAccessFile(f, "r")) {
      FileChannel ch = raf.getChannel();

      ByteBuffer buf = ByteBuffer.allocate(4096);

      ch.read(buf);

      buf.flip();

      for (Charset charset : orderedCharsets) {
        CharsetDecoder decoder = charset.newDecoder();

        decoder.reset();

        try {
          decoder.decode(buf);

          return charset;
        } catch (CharacterCodingException ignored) {
        }
      }
    }

    return Charset.defaultCharset();
  }