code: public static String getMD5Digest(String password) {
  		MessageDigest md = null;
  		try {
  			md = MessageDigest.getInstance("MD5");
  		} catch (NoSuchAlgorithmException e) {
  			e.printStackTrace();
  			return null;
  		}
  		md.update(password.getBytes());
  		byte[] digest = md.digest();
  		StringBuffer sb = new StringBuffer();
  		for (int i : digest) {
  			if (i < 0) {
  				i += 256;
  			}
  			if (i < 16) {
  				sb.append('0');
  			}
  			sb.append(Integer.toHexString(i));
  		}
  		return sb.toString();
  	}
docs: 获取经过MD5加密后的字符串，该加密算法不可逆
  
  @param password
  需要加密的密码
  @return 返回加密后的字符串,失败返回null