MD5方法

private String MD5(String s) {    try {        MessageDigest md = MessageDigest.getInstance("MD5");        byte[] bytes = md.digest(s.getBytes("utf-8"));        return toHex(bytes);    }    catch (Exception e) {        throw new RuntimeException(e);    }}private static String toHex(byte[] bytes) {    final char[] HEX_DIGITS = "0123456789ABCDEF".toCharArray();    StringBuilder ret = new StringBuilder(bytes.length * 2);    for (int i=0; i<bytes.length; i++) {        ret.append(HEX_DIGITS[(bytes[i] >> 4) & 0x0f]);        ret.append(HEX_DIGITS[bytes[i] & 0x0f]);    }    return ret.toString();}