Java CharBuffer mark and reset to set buffer content

import java.nio.ByteBuffer;
import java.nio.CharBuffer;

public class Main {

   public static void main(String[] args) {
      char[] data = "demo2s.com".toCharArray();
      ByteBuffer bb = ByteBuffer.allocate(data.length * 2);

      CharBuffer cb = bb.asCharBuffer();
      cb.put(data);/*from w  w  w .  j a  v a  2s.c  om*/

      System.out.println(cb.rewind());
      symmetricScramble(cb);
      System.out.println(cb.rewind());
      symmetricScramble(cb);
      System.out.println(cb.rewind());
   }
   private static void symmetricScramble(CharBuffer buffer) {
      while (buffer.hasRemaining()) {
         buffer.mark();
         char c1 = buffer.get();
         char c2 = buffer.get();
         buffer.reset();
         buffer.put(c2).put(c1);
      }
   }
}