learning java Encoder and Decoder

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;

public class CharsetTransform {
    public static void main(String[] args) throws CharacterCodingException {
        Charset cn = Charset.forName("GBK");
        CharsetEncoder cnEncoder = cn.newEncoder();
        CharsetDecoder cnDecoder = cn.newDecoder();

        CharBuffer cbuff = CharBuffer.allocate();
        cbuff.put("良红");
        cbuff.flip();
        ByteBuffer bbuff = cnEncoder.encode(cbuff);
        for (var i =; i < bbuff.capacity(); i++){
            System.out.println(bbuff.get(i) + " ");
        }
        System.out.println("\n" + cnDecoder.decode(bbuff));

    }
}

output:

-63
-68
-70
-20 

良红