android下用md5加密一个字符串：

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 public String md5(String s) {
        try {
            // Create MD5 Hash
            MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
            digest.update(s.getBytes());
            byte messageDigest[] = digest.digest();

            // Create HEX String
            StringBuffer hexString = new StringBuffer();
            for (int i = 0; i < messageDigest.length; i++) {
                hexString.append(Integer.toHexString(0xFF & messageDigest[i]));
            }

            return hexString.toString();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }

        return "";
    }