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());
    }