All Packages  Class Hierarchy  This Package  Previous  Next  Index

Class com.monpetitcoin.java.PrisonerGame.Prisoner

java.lang.Object
   |
   +----com.monpetitcoin.java.PrisonerGame.Prisoner

public class Prisoner

extends java.lang.Object

implements com.monpetitcoin.java.PrisonerGame.Pawn

The class implements the Pawn interface, so that the Prisoners can fit on a GameBoard. The GameBoard knows how it wants the Prisoner to draw itself. The Prisoner chooses dynamically a subclass of ShapeDrawer to fit the request of the board.

Version:

1.00, 22 August 2001

Author:

François Suter

See Also:

com.monpetitcoin.java.GameBoard, com.monpetitcoin.java.Pawn, prisoner.shapes.ShapeDrawer

board

DEFAULT_INCENTIVE

DEFAULT_THRESHOLD

gain

game

id

idCounter

incentive

maxNeighbors

neighbors

NO_STATE

oldState

renderer

state

= 1 for honest behavior
= 0 for cheating

threshold

Prisoner(PrisonerGame, GameBoard)

Prisoner(PrisonerGame, GameBoard, double)

Prisoner(PrisonerGame, GameBoard, double, double)

Prisoner(PrisonerGame, GameBoard, double, double, int)

Prisoner(PrisonerGame, GameBoard, double, double, int, double)

This is the most complete constructor.

calculateGain()

This methods is where the Prisoner deals with all its neighbors.

draw(Graphics, int, int, int, int)

drawConclusion()

This method is where the Prisoner decides whether to change its behavior or not.

getGain()

getID()

getIncentive()

getOldState()

getState()

getThreshold()

setNeighbors(Pawn[])

 private static final double DEFAULT_INCENTIVE

 private static final double DEFAULT_THRESHOLD

 private static final int NO_STATE

 private static int idCounter

 private int state

= 1 for honest behavior
= 0 for cheating

 private int oldState

 private int id

 private double gain

 private double incentive

 private double threshold

 private com.monpetitcoin.java.PrisonerGame.GameBoard board

 private com.monpetitcoin.java.PrisonerGame.PrisonerGame game

 private com.monpetitcoin.java.PrisonerGame.Prisoner neighbors[]

 private int maxNeighbors

 private prisoner.shapes.ShapeDrawer renderer

 public Prisoner(com.monpetitcoin.java.PrisonerGame.PrisonerGame game,
                 com.monpetitcoin.java.PrisonerGame.GameBoard board)

 public Prisoner(com.monpetitcoin.java.PrisonerGame.PrisonerGame game,
                 com.monpetitcoin.java.PrisonerGame.GameBoard board,
                 double incentive)

 public Prisoner(com.monpetitcoin.java.PrisonerGame.PrisonerGame game,
                 com.monpetitcoin.java.PrisonerGame.GameBoard board,
                 double incentive,
                 double threshold)

 public Prisoner(com.monpetitcoin.java.PrisonerGame.PrisonerGame game,
                 com.monpetitcoin.java.PrisonerGame.GameBoard board,
                 double incentive,
                 double threshold,
                 int state)

 public Prisoner(com.monpetitcoin.java.PrisonerGame.PrisonerGame game,
                 com.monpetitcoin.java.PrisonerGame.GameBoard board,
                 double incentive,
                 double threshold,
                 int state,
                 double gain)

This is the most complete constructor. All other constructors refer it.

Parameters:

game - callback reference to the currently running game

board - callback reference to the board containing the Prisoner

incentive - variable gain when a dishonest Prisoner cheats an honest one

threshold - excess gain necessary for a Prisoner to change its behavior

state - initial state of the Prisoner (=1 honest, =0 dishonest)

gain - initial gain of the Prisoner

 public int getState()

 public int getOldState()

 public double getGain()

 public double getIncentive()

 public double getThreshold()

 public void draw(java.awt.Graphics g,
                  int x,
                  int y,
                  int width,
                  int height)

 public int getID()

 public void setNeighbors(com.monpetitcoin.java.PrisonerGame.Pawn theNeighbors[])

 public void calculateGain()

This methods is where the Prisoner deals with all its neighbors. The Prisoner loops over its neighbors array and calculates its gain depending on its and its neighbor's behaviors.

At this point, it is important to preserve the state of the Prisoner, by storing it in the oldState member variable. Indeed, the game first asks all Prisoners to calculate their gain. Then each Prisoner in turn must decide whether to change its behavior or not. This decision is based on the neighbors' gains and behaviors. But since Prisoners are called one after the other, when Prisoner n must draw its conclusion, Prisoners 1 to n-1 have already drawn theirs and changed their state. Thus the comparison must be made with the previous game turn's state.

See Also:

drawConclusion

 public void drawConclusion()

This method is where the Prisoner decides whether to change its behavior or not. This is achieved by comparing its gain and behavior with its neighbors' gains and behaviors (the behavior being the one from the previous game turn, as explained in calculateGain()).

The actual algorithm for decision calculates the average gain among all the honest neighbors and all the dishonest neighbors. A decision to change is then taken on two conditions:

1. the other party (the one with the opposite behavior of the Prisoner) has gained significantly more than the Prisoner (i.e. the difference is higher than the threshold);
2. the same party has gained less than the opposing party (note that the Prisoner itself isn't counted in the average of its own party)

This means that even if the opposing party has gained more than itself, the Prisoner will not change its behavior if its party has gained even more than the opposing party. In a sense, the Prisoner is reassured in its behavior by seeing its party come on top.

See Also:

calculateGain

All Packages  Class Hierarchy  This Package  Previous  Next  Index