Regular expression intercepts the contents of a string between two characters

I. Problems

I have a string like A= "Abcdanmcadedcdeefako." So how can I get an array where the items in the array are the middle characters of the letters A and C, that is, the first item is "B", the second "NM", and the third "ded".

Second, the answer

The following is written in C #, Java can also be applied

static void Main (string[] args)
        {
            string a = "Abcdanmcadedcdeefako";
                        Regex reg = new Regex ("(? i) (? <=a) [^a]* (? =c)");//commend by Danielinbiti
            matchcollection mc = Reg. Matches (a);
            foreach (Match m in MC)
            {
                Console.WriteLine (m.value);
            }
        }

If the string is "A1bcdanmca1derdcdeefa1koc"

Need to match between A1 and C, then the regular expression is

(? i) (? <=a1) ((?! A1).) * (? =c)

This is mainly used for pre search and reverse pre search