in flink,how to store mutiple k-v and match them while mapping

there are userID and cardID.When data comes,store it if it cant match cardID, or check its userID.when the user is not match,print a warn including userIDs and cardID.

I try to store them in

class Bean{
  String userID;
  String cardID;
}

Liststate<Bean> liststate;

I can store them,just dont know how to match.

>Solution :

You don`t need to store k-v.
Key your stream by cardId and in keyedProcessFunction keep a state for UserId.
If incoming userId is not same with the userId in the value state, create warning message.