Java regex; conditions on groups

I want to create a regex, where the occurence of one group, depends on whether or not another certain group has been found. I think this is easier to illustrate wit开发者_开发问答h an example!

I want to allow two patterns, illustrated by these two examples: JsJh, JJ. This is not allowed: JsJs, JsJ, JQ.

So if the user types one small letter after the first capital one, the regex expects another small letter after the second capital - but it should not be the same letter as the first one!

I match the first (Js) like this: ([123456789TJQKA]){1}([dsch]?){1} The second capital letter is matched by (\\2).

Now, I cannot seem to find a solution for the last small letter. I can get the small letters to match (which is obv. not what I want), but how do I, if its present, exclude the first letter from the last group, by still allowing (and expecting) one of the three remaining small letters?

Why are you using regular expressions to implement the logic of a card game? Seems pretty crazy... nevertheless it can be done!

s.matches("([123456789TJQKA])([dchs])\\1(?!\\2)[dchs]|([123456789TJQKA])\\3")

Here is a test to verify that it works correctly (and it also documents my assumptions about the special cases that you haven't covered in your question):

public class Test
{
    private static void test(String input, boolean expected)
    {
        boolean result = input.matches("([123456789TJQKA])([dchs])\\1(?!\\2)[dchs]|([123456789TJQKA])\\3");
        if (result != expected)
            throw new RuntimeException("Failed!");
    }

    public static void main(String[] args) throws Exception
    {
        test("JJ", true);
        test("JsJd", true);
        test("11", true);
        test("2c2h", true);

        test("Js", false);
        test("JsJs", false);
        test("JsJ", false);
        test("JQ", false);
        test("1d1d", false);
        test("J", false);
        test("", false);
        test("3d3d", false);
        test("JsJdJ", false);
        test("JsJdJh", false);
        test("1A", false);
    }
}