Think Java, 2nd Edition

Chapter 12. Arrays of Objects

During the next three chapters, we will develop programs that work with playing cards and decks of cards. Here is an outline of the road ahead:

• In this chapter, we define a Card class and write methods that work with cards and arrays of cards.

• In Chapter 13, we define a Deck class that encapsulates an array of cards, and we write methods that operate on decks.

• In Chapter 14, we introduce a way to define new classes that extend existing classes. Then we use Card and Deck to implement the game Crazy Eights.

There are 52 cards in a standard deck. Each card belongs to one of four suits and one of 13 ranks. The suits are Clubs, Diamonds, Hearts, and Spades. The ranks are Ace, 2, 3, 4, 5, 6, 7, 8, 9, 10, Jack, Queen, and King.

If you are unfamiliar with traditional playing cards, now would be a good time to get a deck or read through Wikipedia’s “Standard 52-card deck” entry.

Card Objects

If we want to define a class to represent a playing card, it is pretty clear what the instance variables should be: rank and suit. It is not as obvious what types they should be.

One possibility is a String containing things like "Spade" for suits and "Queen" for ranks. A problem with this choice is that it would not be easy to compare cards to see which had a higher rank or suit.

An alternative is to use integers to encode the ranks and suits. By encode, we don’t mean to encrypt or translate into a secret code. We mean to define a mapping between a sequence of numbers and ...