Stack<Card>[] cards = new Stack<Card>[52];

Stack<Card>[] cards = (Stack<Card>[]) new Stack[52];

List<Stack<Card>> cards = new ArrayList<Stack<Card>>();

Stack<Card>[] decks = new Stack[9];       // Declare
Card c = decks[5].pop();                  // This compiles - java 'knows' the type
Integer i = decks[4].pop();               // This will not compile