Why null pointer?

If the list is null, trying to add an item onto the list will result in the Null pointer error you are getting. To fix this, you need to initilize the cards object like so:

To clarify a little: you can't call a method on a null reference without getting a NullPointerException. With: ... you are calling the "add" method on the "cards" reference. If cards is null then you are calling a method on a null reference. To put it another way, you can't add something to a list which doesn't exist. The list must exist first (as an empty list) before you can add something to it.

Oh whoops, forgot about that specific quirk. List itself is abstract, you will need to chose a specific type of List to initialize. For instance:

ArrayList<Card> cards = new AarrayList<Card>(); Should of course be: ArrayList<Card> cards = new ArrayList<Card>(); :) You can also do: List<Card> cards = new ArrayList<Card>();