title: one to one relationship between classes in java
body: <p>I have to implement following classes in Java SE but I cannot figure out that how can I achieve the one-to-one relationship between ATMCard and Account. I have researched (may be with wrong keywords) but could not find anything. Thank you in advance.. </p>
  
  <p><img src="https://i.stack.imgur.com/aq1QH.jpg" alt="Class diagram, mentioned in the question"></p>