import java.util.ArrayList;
...
ArrayList<Card> hand = new ArrayList<Card>();
To use the ArrayList you have do
hand.get(i); //gets the element at position i
hand.add(obj); //adds the obj to the end of the list
hand.remove(i); //removes the element at position i
hand.add(i, obj); //adds the obj at the specified index
hand.set(i, obj); //overwrites the object at i with the new obj