交换相邻字符（CharBuffer）

摘自thinking in java：

public class UsingBuffers {    private static void symmetricScramble(CharBuffer buffer) {        while (buffer.hasRemaining()) {            buffer.mark();            char c1 = buffer.get();            if(buffer.hasRemaining()) {                char c2 = buffer.get();                buffer.reset();                buffer.put(c2).put(c1);            }else {                buffer.reset();                buffer.put(c1);            }        }    }    public static void main(String[] args) {        char[] data = "UsingBuffers7".toCharArray();        ByteBuffer bb = ByteBuffer.allocate(data.length * 2);        CharBuffer cb = bb.asCharBuffer();        cb.put(data);        System.out.println(cb.rewind());        symmetricScramble(cb);        System.out.println(cb.rewind());    }