java MD5加密 (与php中一致)

 直接上代码 

    private String md5(String txt) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            md.update(txt.getBytes("GBK"));
            StringBuilder buf = new StringBuilder();
            for (byte b : md.digest()) {
                buf.append(String.format("%02x", b & 0xff));
            }
            return buf.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }