Engr 691 Special Topics in Engineering Science Software Architecture Spring Semester 2004 Lecture Notes

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Engr 691Special Topics in Engineering Science
Software ArchitectureSpring Semester
2004Lecture Notes
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Solitaire Case Study (Budd's UOOPJ, Ch. 9)

• This is a set of slides to accompany chapter 9 of
  
• Timothy Budd's textbook
• Understanding Object-Oriented Programming with
  Java,
• Updated Edition
• (Addison-Wesley, 2000)

3
The Solitaire Game

• Good example of inheritance in action
• Constructed from classes for cards, card piles,
  and the game application

4
Class Card

• import java.awt.
• public class Card
• // public constants for card dimensions
• public final static int width 50
• public final static int height 70
• // public constants for card suits
• public final static int heart 0
• public final static int spade 1
• public final static int diamond 2
• public final static int club 3

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Class Card (continued)

• // constructors
• public Card (int sv, int rv)
• s sv
• r rv
• faceup false
• // mutators
• public final void flip()
• faceup ! faceup

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Class Card (continued)

• // accessors
• public final int rank ()
• return r
• public final int suit()
• return s
• public final boolean faceUp()
• return faceup

7
Class Card (continued)

• public final Color color()
• if (faceUp())
• if (suit() heart suit() diamond)
  
• return Color.red
• else
• return Color.black
• return Color.yellow
• public void draw (Graphics g, int x, int y)
  / ... /
• // internal data fields
• private boolean faceup // card
  face exposed?
• private int r
  // card rank
• private int s
  // card suit

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Notes on Class Card

• Class implements playing card abstraction
• Textbook code rearranged into our standard format
• import makes package java.awt available to
  programpart of Java API
• Variables and classes can be used before defined
  (except local variables in methods)

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Notes on Class Card (continued)

• Java has no global variables, constants, or
  enumerated data types
• static data fields (i.e., class variables) used
  for global
• final data fields used for constants assigned
  once, then not redefined
• Three internal data fields
• rank and suit are read-only accessors but no
  mutators
• faceup can be modified flip() mutator
• draw is complex method accessor with side
  effects
• final methods accessors rank(), suit(),
  faceup(), and color(), and mutator flip()
• cannot be overridden in subclasses
• can be optimized expanded inline like a macro
  efficient but inhibits reuse!
• draw is not final implementation may be
  somewhat platform dependent

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Card Images

• See Figure 9.3 on page 145 of Budd's
• UOOPJ.

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Method draw

• import java.awt.
• public class Card
• // ...
• public void draw (Graphics g, int x, int y)
• String names "A", "2", "3", "4",
  "5", "6", "7", "8", "9",
• "10", "J",
  "Q", "K"
• // clear rectangle, draw border
• g.clearRect(x, y, width, height)
• g.setColor(Color.blue)
• g.drawRect(x, y, width, height)
• // draw body of card
• g.setColor(color())

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Method draw (continued)

• if (faceUp())
• g.drawString(namesrank(), x3, y15)
• if (suit() heart)
• g.drawLine(x25, y30, x35, y20)
  g.drawLine(x35, y20, x45, y30)
• g.drawLine(x45, y30, x25, y60)
  g.drawLine(x25, y60, x5, y30)
• g.drawLine(x5, y30, x15, y20)
  g.drawLine(x15, y20, x25, y30)
• else if (suit() spade)
• g.drawLine(x25, y20, x40, y50)
  g.drawLine(x40, y50, x10, y50)
• g.drawLine(x10, y50, x25, y20)
  g.drawLine(x23, y45, x20, y60)
• g.drawLine(x20, y60, x30, y60)
  g.drawLine(x30, y60, x27, y45)
• else if (suit() diamond)
• g.drawLine(x25, y20, x40, y40)
  g.drawLine(x40, y40, x25, y60)
• g.drawLine(x25, y60, x10, y40)
  g.drawLine(x10, y40, x25, y20)
• else if (suit() club)
• g.drawOval(x20, y25, 10, 10)
  g.drawOval(x25, y35, 10, 10)
• g.drawOval(x15, y35, 10, 10)
  g.drawLine(x23, y45, x20, y55)
• g.drawLine(x20, y55, x30, y55)
  g.drawLine(x30, y55, x27, y45)

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Method draw (continued)

• else
• // face down
• g.drawLine(x15, y5, x15, y65)
• g.drawLine(x35, y5, x35, y65)
• g.drawLine(x5, y20, x45, y20)
• g.drawLine(x5, y35, x45, y35)
• g.drawLine(x5, y50, x45, y50)

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Notes on Method draw

• Displays the card on screen
• Parameter is current graphics context
• argument is object of class java.awt.Graphics
• class Graphics in Java API provides many drawing
  primitives
• methods for printing bit-maps available for more
  sophisticated visuals
• Constants such as Color.red and Color.black
  defined in class java.awt.Color
• draw is instance method every card responsible
  for drawing itself

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The Game

• See Figure 9.4 on page 145 of Budd's UOOPJ.

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Class CardPile

• import java.awt.
• import java.util.Stack
• import java.util.EmptyStackException
• public class CardPile
• // constructors
• public CardPile (int xl, int yl)
• x xl
• y yl
• thePile new Stack()

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Class CardPile (continued)

• //mutators
• public final Card pop()
• try
• return (Card) thePile.pop()
• catch (EmptyStackException e)
• return null
• public void addCard (Card aCard) // sometimes
  overridden
• thePile.push(aCard)
• public void select (int tx, int ty) // sometimes
  overridden
• / do nothing /

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Class CardPile (continued)

• // accessors
• public final Card top()
• return (Card) thePile.peek()
• public final boolean isEmpty()
• return thePile.empty()
• public boolean includes (int tx, int ty) //
  sometimes overridden
• return x lt tx tx lt x Card.width
• y lt ty ty lt y Card.height
• public boolean canTake (Card aCard) // sometimes
  overridden
• return false
• public void display (Graphics g) // sometimes
  overridden
• g.setColor(Color.blue)

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Class CardPile (continued)

• // protected data fields
• // coordinates of the card pile
• protected int x
• // (x,y) is upper left corner
• protected int y
• // cards in the pile
• protected Stack thePile

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Notes on Class CardPile

• Implementation of card deck abstraction
• base class extended for specific behaviors
• Uses generic container Stack from Java API for
  pile of cards
• empty initially
• Stack operations implement Card operations
  adapter pattern
• Cast objects back to Card when taken from stack
• Uses global symbolic constants Card.width and
  Card.height
• access to static fields using class name, not
  instance name (actually, either works)
• pop, top, and isEmpty implementation for
  subclasses -- final methods
• addCard, select, includes, canTake, and display
  part of abstraction, but implementation varies
  among subclasses
• protected data fields accessible by subclasses
• Instructor's comment
• protected data fields usually bad practice
  trusts subclasses (perhaps in different package)
  to manipulate internal fields correctly safer
  to provide appropriate protected mutators and
  accessors instead (perhaps final)

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Informal Specification of CardPile's Non-final
Methods

• Methods may need to be overridden to give the
  card deck the appropriate behaviors.
• addCard(c)
• adds card c to the card pile
• select(x,y)
• performs an action in response to mouse click at
  (x,y)
• includes(x,y)
• determines whether (x,y) within boundary of the
  pile
• canTake(c)
• determines whether the pile can take card c
  (according to the rules governing the pile)
• display(g)
• displays the pile using graphics context g

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Class SuitPile

• class SuitPile extends CardPile
• // constructors
• public SuitPile (int x, int y)
• super(x, y)
• // accessors
• public boolean canTake (Card aCard)
• // overrides parent
• if (isEmpty())
• return aCard.rank() 0
• Card topCard top()
• return (aCard.suit()
  topCard.suit())
• (aCard.rank() 1
  topCard.rank())

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Notes on Class SuitPile

• Represents one of the (4) piles of cards at top
  of playing surface built up in suit from Ace
  (1) to King (13)
• Keyword extends indicates inheritance from
  CardPile
• super indicates parent in constructor used to
  call parent's constructor for initialization
  first statement only
• Method canTake overridden by replacement
  canTake if pile empty or card is next higher of
  same suit

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Class DeckPile

• import java.util.Random
• class DeckPile extends CardPile
• // constructors
• public DeckPile (int x, int y)
• // first initialize parent
• super(x, y)
• // then create the new deck, first put
  them into a local pile
• for (int i 0 i lt 4 i)
• for (int j 0 j lt 12 j)
• addCard(new Card(i, j))
• // then shuffle the cards
• Random generator new Random()
• for (int i 0 i lt 52 i)
• int j Math.abs(generator.nextInt
  () 52)
• // swap the two card values
• Object temp thePile.elementAt(i)
  
• thePile.setElementAt(thePile.eleme
  ntAt(j), i)
• thePile.setElementAt(temp, j)

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Notes on Class DeckPile

• Represents the original deck of cards
• Uses super in constructor for basic
  initialization, new code for specific
  initialization
• Accesses static (class) methods absolute value
  function Math.abs()
• Overrides method select by replacement if pile
  nonempty, add top card to discard pile
• Java API Stack extends Vector select uses the
  "ranked sequence" methods of Vector
• Instructor's comment
• Stack extending Vector is poor design in the Java
  API! Similarly, the choice of Stack is a
  questionable design. Better to just use Vector
  directly

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Notes on Class DeckPile (continued)

• Accesses utility class java.util.Random to
  generate pseudo-random numbers
• Accesses static (class) variables to share single
  copies
• Solitaire.discardPile
• Author has only one discard pile, so made this
  class access that instance directly
• Instructor's comment
• Hard-coding of reference to static discard pile
  inhibits reusability of the deck
• Probably better to pass discard deck to
  constructor of DeckPile, store reference,
  manipulate it

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Notes on Class DeckPile(continued)

• Manipulates protected field thePile from parent
  class CardPile
• Possible alternatives to use of protected data
  fields
• Add (protected?) "ranked sequence" get and set
  operations to CardPile abstraction?
• Add constructor or (protected?) set operation to
  CardPile that takes a sequence (vector, array,
  etc.) of cards to (re)initialize pile? get
  method?
• Add shuffle operation to CardPile abstraction?

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Class DiscardPile

• import java.util.Random
• class DiscardPile extends CardPile
• // constructors
• public DiscardPile (int x, int y)
• super (x, y)
• // mutators
• public void addCard (Card aCard)
• if (! aCard.faceUp())
• aCard.flip()
• super.addCard(aCard)

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Class DiscardPile (continued)

• //mutators
• public void select (int tx, int ty)
• if (isEmpty())
• return
• Card topCard pop()
• for (int i 0 i lt 4 i)
• if (Solitaire.suitPilei.canTake(topCa
  rd))
• Solitaire.suitPilei.addCard(top
  Card)
• return
• for (int i 0 i lt 7 i)
• if (Solitaire.tableaui.canTake(topCard
  ))
• Solitaire.tableaui.addCard(topC
  ard)
• return
• // nobody can use it, put it back on our
  list
• addCard(topCard)

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Notes on Class DiscardPile

• Represents the discard pile in a Solitaire game
• Constructor refines parent's constructor uses
  super call in initialization
• select method overrides and replaces one in
  parent
• checks whether topmost card can be played any
  suit pile or tableau pile
• addCard method overrides and refines one in
  parent
• executes parent method (super.addCard), but also
  adds new behavior
• flips card faceup when put on discard pile
• Hard-coded access to static variables for the (4)
  suit piles and (7) tableau piles
• probably better to pass these to constructor,
  store references, and manipulate via local
  references

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Class TablePile

• import java.util.Enumeration
• class TablePile extends CardPile
• // constructors
• public TablePile (int x, int y, int c)
• // initialize the parent class
• super(x, y)
• // then initialize our pile of cards
• for (int i 0 i lt c i)
• addCard(Solitaire.deckPile.pop())
• // flip topmost card face up
• top().flip()

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Class TablePile (continued)

• // mutators
• public void select (int tx, int ty)
• if (isEmpty()) return
• // if face down, then flip
• Card topCard top()
• if (! topCard.faceUp())
• topCard.flip()
• return
• // else see if any suit pile can take card
• topCard pop()
• for (int i 0 i lt 4 i)
• if (Solitaire.suitPilei.canTake(topCard))
  
• Solitaire.suitPilei.addCard(topCard
  )
• return
• // else see if any other table pile can
  take card
• for (int i 0 i lt 7 i)
• if (Solitaire.tableaui.canTake(topCard))
  
• Solitaire.tableaui.addCard(topCard)
  
• return

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Class TablePile (continued)

• // accessors
• public boolean canTake (Card aCard)
• if (isEmpty())
• return aCard.rank() 12
• Card topCard top()
• return (aCard.color() !
  topCard.color())
• (aCard.rank()
  topCard.rank() - 1)
• public boolean includes (int tx, int ty)
• // don't test bottom of card
• return x lt tx tx lt x Card.width
  y lt ty
• public void display (Graphics g)
• int localy y
• for (Enumeration e thePile.elements()
  e.hasMoreElements())
• Card aCard (Card)
  e.nextElement()
• aCard.draw (g, x, localy)
• localy 35

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Notes on Class TablePile

• Represents one of the (7) tableau piles on the
  lower part of the playing surface
• Initialized with cards from deck constructor
  argument gives number needed
• Top card is face up
• Add card to empty pile only if King
• Add card to nonempty pile only if opposite color
  to top and one rank lower
• Selection action moves any cards from this table
  pile to suit pile or another table pile
• Uses super in constructor for basic
  initialization, new code for specific
  initialization
• Methods select, canTake, includes, and display
  override and replace ones in parent
• Method display
• Uses java.util.Enumeration object returned by the
  Stack to iterate through the tableau pile
• Displays each card slightly offset from the one
  below it
• Accesses protected field thePile from parent
  class CardPile
• Perhaps define (protected?) elements()
  method in CardPile to return a pile-Enumeration
  object to avoid protected fields
• Another alternative method to return cards
  in pile as sequence (e.g., array or vector)

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The Game Class Solitaire

• import java.awt.
• import java.awt.event.
• public class Solitaire
• // public class variables for the various
  card piles of game
• static public DeckPile deckPile
• static public DiscardPile discardPile
• static public TablePile tableau
• static public SuitPile suitPile
• // single array to alias all above piles --
  aids polymorphism
• static public CardPile allPiles

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The Game Class Solitaire (continued)

• // application entry point
• static public void main (String args)
• Solitaire world new Solitaire()
• // constructors
• public Solitaire ()
• window new SolitaireFrame()
• init()
• window.show()

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The Game Class Solitaire (continued)

• //mutators
• public void init ()
• // first allocate the arrays
• allPiles new CardPile13
• suitPile new SuitPile4
• tableau new TablePile7
• // then fill them in
• allPiles0 deckPile new DeckPile(335,
  30)
• allPiles1 discardPile new
  DiscardPile(268, 30)
• for (int i 0 i lt 4 i)
• allPiles2i suitPilei new
  SuitPile(15 (Card.width10) i, 30)
• for (int i 0 i lt 7 i)
• allPiles6i tableaui
• new TablePile(15
  (Card.width5) i, Card.height 35, i1)

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The Game Class Solitaire (continued)

• // inner classes
• private class SolitaireFrame extends Frame
• / expanded later /
• // internal data fields
• private Frame window// the application
  window

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Notes on Class Solitaire

• Class declares and allocates class (static)
  variables for piles of cards on playing surface
• Class sets up allpiles array to "alias" all other
  piles, regardless of subclass
• Control goes initially to class method main
• main creates an instance of Solitaire application
  (its only action)
• Solitaire constructor creates window for
  application, initializes the playing surface, and
  displays window
• SolitaireFrame is an inner class
• inner class (from the glossary to Budd's
  UOOPJ textbook)
• a class definition that appears inside another
  class. Inner classes are allowed access to both
  the private data fields and the methods of the
  surrounding class. Inner classes are frequently
  used in building listener objects for handling
  events.
• SolitaireFrame manages the application window

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Inner Class SolitaireFrame

• // part of Class Solitaire
• private class SolitaireFrame extends Frame
• private class RestartButtonListener
  implements ActionListener
• public void actionPerformed
  (ActionEvent e)
• init()
• window.repaint()

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Inner Class SolitaireFrame(continued)

• private class MouseKeeper extends MouseAdapter
• public void mousePressed (MouseEvent e)
• int x e.getX()
• int y e.getY()
• for (int i 0 i lt 13 i)
• if (allPilesi.includes(x,
  y))
• allPilesi.select(x,
  y)
• repaint()

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Inner Class SolitaireFrame(continued)

• public SolitaireFrame()
• setSize(600, 500)
• setTitle("Solitaire Game")
• addMouseListener (new MouseKeeper())
• Button restartButton new Button("New
  Game")
• restartButton.addActionListener(
• new RestartButtonListener())
  
• add("South", restartButton)
• public void paint(Graphics g)
• for (int i 0 i lt 13 i)
• allPilesi.display(g)

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Notes on Class SolitaireFrame

• GUI window for the Solitaire game application
• Extends java.awt.Frame class
• Event-driven program system GUI manager in
  control, user code "called back" in response to
  GUI events
• SolitaireFrame constructor
• sets window size, title
• adds mouse listener "callback" code to respond to
  mouse events
• adds restart button at bottom of window ("South")
  and "callback" code to respond to button events

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Notes on Class SolitaireFrame (continued)

• Inner class MouseKeeper's method mousePressed
  called on mouse click event
• determines which pile selected
• performs select operation for that pile
• note use of polymorphism
• action depends on pile type (i.e., on which
  subclass)
• repaints window
• Inner class RestartButtonListener method
  actionPerformed called on button event
• reinitializes game
• repaints window
• Method paint of SolitaireFrame called by GUI when
  frame needs to be displayed
• note use of polymorphism