md5加密

public class MD5Util {

    /**
     * MD5加密
     *
     * @param str
     * @return
     * @throws NoSuchAlgorithmException
     * @throws UnsupportedEncodingException
     */
    public static String md5(String str) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            byte[] bytes = md.digest(str.getBytes("utf-8"));
            return toHex(bytes);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * 二进制转换为十六进制
     *
     * @param bytes
     * @return
     */
    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();
    }

    /**
     * 加盐MD5
     *
     * @param str
     * @param salt
     * @return
     */
    public static String md5salt(String str, String salt) {
        return md5(str + salt);
    }

    /**
     * 两次加密
     *
     * @param str
     * @return
     */
    public static String md5_double(String str) {
        return md5(md5(str));
    }

    /**
     * 两次加密再加盐
     *
     * @param str
     * @param salt
     * @return
     */
    public static String md5salt_double(String str, String salt) {
        return md5(md5salt(str, salt));
    }


    public static void main(String[] args) {
        String str = "123456";
        String salt = "zxc";

        System.out.println("md5(str) = " + md5(str));
        System.out.println("md5salt(str,salt) = " + md5salt(str, salt));
        System.out.println("md5_double(str) = " + md5_double(str));
        System.out.println("md5salt_double(str,salt) = " + md5salt_double(str, salt));

    }