O-O Pig Game

Pig is a folk jeopardy dice game with simple rules: Two players race to reach 100 points. Each turn, a player repeatedly rolls a die until either a 1 ("pig") is rolled or the player holds and scores the sum of the rolls (i.e. the turn total). At any time during a player's turn, the player is faced with two decisions:

• roll - If the player rolls a
  • 1: the player scores nothing and it becomes the opponent's turn.
  • 2 - 6: the number is added to the player's turn total and the player's turn continues.
• hold - The turn total is added to the player's score and it becomes the opponent's turn.

Problem:  Create an object-oriented implementation of a game of Pig where the user plays against a "hold at 20 or goal" computer player that rolls until a 1 ("pig") is rolled, or the turn total is greater than or equal to 20, or the score plus the turn total is greater than or equal to 100.  The first player is chosen randomly.

O-O Design Constraints:

BlueJ UML diagram:

Although one need not implement in Java, the object-oriented specification is supplied via HTML Javadoc documentation.  The global input/output specification is given here:

Input Format:  An empty input (i.e., Enter) indicates that the user wishes to roll.  Any entered line of non-zero length indicates that the user wishes to hold.

Output Format:

• Before the game, randomly select which player the user will be, and print the line "You will be player #.", where # is the user's player number. Then, print an instruction line "Enter nothing to roll; enter anything to hold."
• Before each turn, print a line with "Player 1 score: " and player 1's score.  Print another line with "Player 2 score: " and player 2's score.  Finally, print a line with "It is player #'s turn.", where "#" is replaced by the current player number.  Play starts with player 1 and then alternates.
• For each roll, print a line with "Roll: " and the random die roll value (1-6).
• For each non-"pig" roll 2-6 on the user's turn, prompt the user with "Turn total: ", the turn total, a tab, and "Roll/Hold? ".
• After a "pig" roll of 1, or a "hold", print a line with "Turn total: " followed by the turn total.  In the case of a "pig", this turn total is 0.  Then, print a line with "New score: " followed by the new score for the current player.

Sample Transcript (input underlined):

You will be player 2.
Enter nothing to roll; enter anything to hold.
Player 1 score: 0
Player 2 score: 0
It is player 1's turn.
Roll: 5
Roll: 3
Roll: 5
Roll: 1
Turn total: 0
New score: 0
Player 1 score: 0
Player 2 score: 0
It is player 2's turn.
Roll: 6
Turn total: 6 	Roll/Hold? (Enter)
Roll: 5
Turn total: 11 	Roll/Hold? (Enter)
Roll: 6
Turn total: 17 	Roll/Hold? (Enter)
Roll: 2
Turn total: 19 	Roll/Hold? (Enter)
Roll: 2
Turn total: 21 	Roll/Hold? h
Turn total: 21
New score: 21
Player 1 score: 0
Player 2 score: 21
It is player 1's turn.
Roll: 5
Roll: 6
Roll: 3
Roll: 5
Roll: 1
Turn total: 0
New score: 0
Player 1 score: 0
Player 2 score: 21
It is player 2's turn.
Roll: 6
Turn total: 6 	Roll/Hold? (Enter)
Roll: 6
Turn total: 12 	Roll/Hold? (Enter)
Roll: 2
Turn total: 14 	Roll/Hold? (Enter)
Roll: 6
Turn total: 20 	Roll/Hold? h
Turn total: 20
New score: 41
Player 1 score: 0
Player 2 score: 41
It is player 1's turn.
Roll: 3
Roll: 3
Roll: 6
Roll: 4
Roll: 4
Turn total: 20
New score: 20
Player 1 score: 20
Player 2 score: 41
It is player 2's turn.
Roll: 3
Turn total: 3 	Roll/Hold? (Enter)
Roll: 3
Turn total: 6 	Roll/Hold? (Enter)
Roll: 2
Turn total: 8 	Roll/Hold? (Enter)
Roll: 2
Turn total: 10 	Roll/Hold? (Enter)
Roll: 4
Turn total: 14 	Roll/Hold? (Enter)
Roll: 2
Turn total: 16 	Roll/Hold? (Enter)
Roll: 4
Turn total: 20 	Roll/Hold? h
Turn total: 20
New score: 61
Player 1 score: 20
Player 2 score: 61
It is player 1's turn.
Roll: 5
Roll: 1
Turn total: 0
New score: 20
Player 1 score: 20
Player 2 score: 61
It is player 2's turn.
Roll: 3
Turn total: 3 	Roll/Hold? (Enter)
Roll: 3
Turn total: 6 	Roll/Hold? (Enter)
Roll: 5
Turn total: 11 	Roll/Hold? (Enter)
Roll: 2
Turn total: 13 	Roll/Hold? (Enter)
Roll: 6
Turn total: 19 	Roll/Hold? h
Turn total: 19
New score: 80
Player 1 score: 20
Player 2 score: 80
It is player 1's turn.
Roll: 3
Roll: 1
Turn total: 0
New score: 20
Player 1 score: 20
Player 2 score: 80
It is player 2's turn.
Roll: 2
Turn total: 2 	Roll/Hold? (Enter)
Roll: 2
Turn total: 4 	Roll/Hold? (Enter)
Roll: 4
Turn total: 8 	Roll/Hold? (Enter)
Roll: 2
Turn total: 10 	Roll/Hold? (Enter)
Roll: 3
Turn total: 13 	Roll/Hold? (Enter)
Roll: 6
Turn total: 19 	Roll/Hold? (Enter)
Roll: 5
Turn total: 24 	Roll/Hold? h
Turn total: 24
New score: 104

Extra Exercises:

1. Use an alternative computer play policy.  Let i be the player's score, j be the opponent's score, and k be the current turn total.  Some alternative play policies:

• Hold at 25 or goal - Hold at the lesser of 25 and 100 - i.
• 4 Scoring Turns - Let t be the number of turns in which a player has held so far.  Hold at floor((100 - i)/(4 - t)).
• Score Base, Keep Pace, and End Race - If i >= 69 or j >= 69, roll for the goal.  Otherwise, hold at the greater of 19 and j - 14.
• Keep Pace and End Race - If i >= 71 or j >= 71, roll for the goal.  Otherwise, hold at 21 + round((j - i) / 8).

2. Allow play of multiple games, alternating the starting player and computing win statistics.

Todd Neller