Unhelpful behaviour of Java ChsrsetEncoder

Encode.java

package test;

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

public class Encode {

    /**
     * @param args
     */
    public static void main(String[] args) {
        String s = "0123456789\nABCDEFG\n風, 薔薇, バズ\n";
        System.out.println("String length: " + s.length());
        
        try {
            CharsetEncoder enc = Charset.forName("UTF-8").newEncoder();

            CharBuffer charbuf = CharBuffer.wrap(s);
            System.out.println("Charbuf pos: " + charbuf.position() + " limit: " + charbuf.limit());
            
            ByteBuffer bytebuf = enc.encode(charbuf);
            System.out.println("Bytebuf pos: " + bytebuf.position() + " limit: " + bytebuf.limit());
        } catch (CharacterCodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

Stdout

String length: 29
Charbuf pos: 0 limit: 29
Bytebuf pos: 0 limit: 39