# problem1.txt
# Dan R. K. Ports <drkp@mit.edu>
# 6.170 PS1-1, 2004/02/07

1. CLUBS, DIAMONDS, HEARTS, and SPADES are static so that one object
   corresponding to each suit is created as part of the class, rather
   than as part of each CardSuit object.

2. Using a separate class rather than integer constants makes it
   possible to distinguish a card suit from any other integer
   value. It also allows other methods to be added (for suit icons,
   etc).

3. this can not be null. If the constructor or some other method is
   being called, then it is referring to some object, and the this
   pointer is set.

4. The constructors are private so that no CardValue or CardSuit
   objects can be instantiated except for the static variables in the
   class.

5. The only CardValue and CardSuit objects are the static variables
   created in their respective classes, which are all different, so
   comparing the addresses (as the default Object.equals method does)
   is an acceptable test for equality.

6. Implementing the Comparable interface allows the Java Collections
   framework to understand the proper ordering of CardValue and
   CardSuit objects, and thus makes it easy to sort them.

7. The ordering of a Deck is significant (since decks of cards are
   shuffled, dealt from, etc). Thus, it is necessary to use an
   unsorted collection to represent one. A Hand does not have any
   particular ordering, and the cards are generally returned in sorted
   order, so it is reasonable to use a sorted collection.