GetChatMember getMember = new GetChatMember();
getMember.setChatId(the_id_of_the_chat); //like the id of the group
getMember.setUserId(user_id); //the id of the specific user
//since the API method GetChatMember is returning a ChatMember object on succes,
// you can try to retrieve it
ChatMember theChatMember = execute(getMember);