Starting Out with Java: From Control Structures through Objects

1

• Starting Out with Java From Control Structures
  through Objects
• 5th edition
• By Tony Gaddis
• Source Code Chapter 6

2

• Code Listing 6-1 (ObjectDemo.java)
• 1 import java.util.Scanner //
  Needed for the Scanner class
• 2 import java.util.Random // Needed for the
  Random class
• 3 import java.io. // Needed for file I/O
  classes
• 4
• 5 /
• 6 This program writes random numbers to a file.
• 7 /
• 8
• 9 public class ObjectDemo
• 10
• 11 public static void main(String args) throws
  IOException
• 12
• 13 int maxNumbers // Max number of random
  numbers
• 14 int number // To hold a random number
• 15
• 16 // Create a Scanner object for keyboard
  input.
• 17 Scanner keyboard new Scanner(System.in)
• 18

3

• 24
• 25 // Get the number of random numbers to
  write.
• 26 System.out.print("How many random numbers
  should I write? ")
• 27 maxNumbers keyboard.nextInt()
• 28
• 29 // Write the random numbers to the file.
• 30 for (int count 0 count lt maxNumbers
  count)
• 31
• 32
• 33 number rand.nextInt()
• 34
• // Write the random integer to
  the file.
• 36 outputFile.println(number)
• 37
• 38
• 39 // Close the file.
• 40 outputFile.close()

4

• Code Listing 6-2 (Rectangle.java)
• 1 /
• 2 Rectangle class, phase 1
• 3 Under construction!
• 4 /
• 5
• 6 public class Rectangle
• 7
• 8 private double length
• 9 private double width
• 10
• 11 /
• 12 The setLength method stores a value in the
• 13 length field.
• 14 _at_param len The value to store in length.
• 15 /
• 16
• 17 public void setLength( double len )
• 18

5

• Code Listing 6-3 (LengthDemo.java)
• 1 /
• 2 This program demonstrates the Rectangle
  class's
• 3 setLength method.
• 4 /
• 5
• 6 public class LengthDemo
• 7
• 8 public static void main(String args)
• 9
• 10 // Create a Rectangle object.
• 12 Rectangle box new Rectangle() //
  Constructor method?
• 13
• 14
• 15 System.out.println("Sending the value 10.0 "
  
• 16 "to the setLength method.")
• 17
• // Call the box object's setLength method.

6

• 20
• // Indicate we are done.
• 22 System.out.println("Done.")
• 23 // end main
• 24 // end class
• Program Output
• Sending the value 10.0 to the setLength method.
• Done.

7

• Code Listing 6-4 (Rectangle.java)
• 1 /
• 2 Rectangle class, phase 2
• 3 Under construction!
• 4 /
• 5
• 6 public class Rectangle
• 7
• 8 private double length
• 9 private double width
• 10
• 11 /
• 12 The setLength method stores a value in the
• 13 length field.
• 14 _at_param len The value to store in length.
• 15 /
• 16
• 17 public void setLength( double len )
• 18

8

• 22 /
• 23 The setWidth method stores a value in the
• 24 width field.
• 25 _at_param w The value to store in width.
• 26 /
• 27
• 28 public void setWidth(double w)
• 29
• 30 width w
• 31
• 32

9

• Code Listing 6-5 (Rectangle.java)
• 1 /
• 2 Rectangle class, phase 3
• 3 Under construction !
• 4 /
• 5
• 6 public class Rectangle
• 7
• 8 private double length
• 9 private double width
• 10
• 11 /
• 12 The setLength method stores a value in the
• 13 length field.
• 14 _at_param len The value to store in length.
• 15 /
• 16
• 17 public void setLength(double len)
• 18

10

• 22 /
• 23 The setWidth method stores a value in the
• 24 width field.
• 25 _at_param w The value to store in width.
• 26 /
• 27
• 28 public void setWidth(double w)
• 29
• 30 width w
• 31
• 32
• 33 /
• 34 The getLength method returns a Rectangle
• 35 object's length.
• 36 _at_return The value in the length field.
• 37 /
• 38
• 39 public double getLength()

11

• 44 /
• 45 The getWidth method returns a Rectangle
• 46 object's width.
• 47 _at_return The value in the width field.
• 48 /
• 49
• 50 public double getWidth()
• 51
• 52 return width
• 53
• 54

12

• Code Listing 6-6 (LengthWidthDemo.java)
• 1 /
• 2 This program demonstrates the Rectangle
  class's
• 3 setLength, setWidth, getLength, and getWidth
  methods.
• 4 /
• 5
• 6 public class LengthWidthDemo
• 7
• 8 public static void main(String args)
• 9
• 10 // Create a Rectangle object.
• 11 Rectangle box new Rectangle()
• 12
• 13 // Call the object's setLength method,
  passing 10.0
• 14 // as an argument.
• 15 box.setLength(10.0)
• 16
• 17 // Call the object's setWidth method,
  passing 20.0
• 18 // as an argument.

13

• // Display the object's length and width.
• 22 System.out.println("The box's length is "
• 23 box.getLength())
• 24 System.out.println("The box's width is "
• 25 box.getWidth())
• 26
• 27
• Program Output
• The box's length is 10.0
• The box's width is 20.0

14

• Code Listing 6-7 (Rectangle.java)
• 1 /
• 2 Rectangle class, phase 4
• 3 Under construction!
• 4 /
• 5
• 6 public class Rectangle
• 7
• 8 private double length
• 9 private double width
• 10
• 11 /
• 12 The setLength method stores a value in the
• 13 length field.
• 14 _at_param len The value to store in length.
• 15 /
• 16
• 17 public void setLength( double len )
• 18

15

• 22 /
• 23 The setWidth method stores a value in the
• 24 width field.
• 25 _at_param w The value to store in width.
• 26 /
• 27
• 28 public void setWidth( double w )
• 29
• 30 width w
• 31
• 32
• 33 /
• 34 The getLength method returns a Rectangle
• 35 object's length.
• 36 _at_return The value in the length field.
• 37 /
• 38
• 39 public double getLength()

16

• 44 /
• 45 The getWidth method returns a Rectangle
• 46 object's width.
• 47 _at_return The value in the width field.
• 48 /
• 49
• 50 public double getWidth()
• 51
• 52 return width
• 53
• 54
• 55 /
• 56 The getArea method returns a Rectangle
• 57 object's area.
• 58 _at_return The product of length times width.
• 59 /
• 60
• 61 public double getArea() // What is
  Stale data?
• 62

17

• Code Listing 6-8 (RectangleDemo.java)
• 1 /
• 2 This program demonstrates the Rectangle
  class's
• 3 setLength, setWidth, getLength, getWidth, and
• 4 getArea methods.
• 5 /
• 6
• 7 public class RectangleDemo
• 8
• 9 public static void main(String args)
• 10
• // Create a Rectangle object.
• 12 Rectangle box new Rectangle()
• 13
• 15 box.setLength(10.0)
• 16 box.setWidth(20.0)
• 17

18

• 21
• // Display the width.
• 23 System.out.println("The box's width is "
• 24 box.getWidth())
• 25
• // Display the area.
• 27 System.out.println("The box's area is "
• 28 box.getArea())
• 29
• 30
• Program Output
• The box's length is 10.0
• The box's width is 20.0

19

• Code Listing 6-9 (RoomAreas.java)
• 1 import javax.swing.JOptionPane
• 2
• 3 /
• 4 This program creates three instances of the
• 5 Rectangle class.
• 6 /
• 7
• 8 public class RoomAreas
• 9
• 10 public static void main(String args)
• 11
• 12 double number // To hold a
  number
• 13 double totalArea // The total
  area
• 14 String input // To hold user input
• 15
• 16 // Create three Rectangle objects.

20

• 22 input JOptionPane.showInputDialog("What is
  the "
• 23 "kitchen's length?")
• 24 number Double.parseDouble(input)
• kitchen.setLength(number)
• 26 input JOptionPane.showInputDialog("What is
  the "
• 27 "kitchen's width?")
• 28 number Double.parseDouble(input)
• kitchen.setWidth(number)
• 30
• // Get and store the dimensions of the bedroom.
• 32 input JOptionPane.showInputDialog("What is
  the "
• 33 "bedroom's length?")
• 34 number Double.parseDouble(input)
• bedroom.setLength(number)

21

• 42 input JOptionPane.showInputDialog("What is
  the "
• 43 "den's length?")
• 44 number Double.parseDouble(input)
• 45 den.setLength(number)
• 46 input JOptionPane.showInputDialog("What is
  the "
• 47 "den's width?")
• 48 number Double.parseDouble(input)
• 49 den.setWidth(number)
• 52 totalArea kitchen.getArea()
  bedroom.getArea()
• 53 den.getArea()
• 54
• 56 JOptionPane.showMessageDialog(null, " "The
  total area
• 57 "of the rooms is " totalArea)
• 58
• 59 System.exit(0)
• 60

22

• Code Listing 6-10 (Rectangle.java)
• 1 /
• 2 Rectangle class, phase 5
• 3 /
• 4
• 5 public class Rectangle
• 6
• 7 private double length
• 8 private double width
• 9
• 10 /
• 11 Constructor
• 12 _at_param len The length of the rectangle.
• 13 _at_param w The width of the rectangle.
• 14 /
• 15
• 16 public Rectangle( double len, double w )
• 17
• 18 length len

23

• Code Listing 6-11 (ConstructorDemo.java)
• 1 /
• 2 This program demonstrates the Rectangle
  class's
• 3 constructor.
• 4 /
• 5
• 6 public class ConstructorDemo
• 7
• 8 public static void main(String args)
• 9
• 10 // Create a Rectangle object, passing 5.0
  and
• // 15.0 as arguments to the
  constructor.
• 12 Rectangle box new Rectangle( 5.0, 15.0 )
• 13
• 14 // Display the length.
• 15 System.out.println("The box's length is "
• 16 box.getLength())
• 17

24

• 22 // Display the area.
• 23 System.out.println("The box's area is "
• 24 box.getArea())
• 25
• 26
• Program Output
• The box's length is 5.0
• The box's width is 15.0
• The box's area is 75.0

25

• Code Listing 6-12 (CellPhone.java)
• 1 /
• 2 The CellPhone class holds data about a cell
  phone.
• 3 /
• 4
• 5 public class CellPhone
• 6
• 7 // Fields
• 8 private String manufact
  // Manufacturer
• 9 private String model
  // Model
• 10 private double retailPrice
  // Retail price
• 11
• 12 /
• 13 Constructor
• 14 _at_param man The phone's manufacturer.
• 15 _at_param mod The phone's model number.
• 16 _at_param price The phone's retail price.
• 17 /
• 18

26

• 24
• 25
• 26 /
• 27 The setManufact method sets the phone's
• 28 manufacturer name.
• 29 _at_param man The phone's manufacturer.
• 30 /
• 31
• 32 public void setManufact( String man )
• 33
• 34 manufact man
• 35
• 36
• 37 /
• 38 The setMod method sets the phone's
• 39 model number.
• 40 _at_param mod The phone's model number.
• 41 /

27

• 47
• 48 /
• 49 The setRetailPrice method sets the phone's
• 50 retail price.
• 51 _at_param price The phone's retail price.
• 52 /
• 53
• 54 public void setRetailPrice( double price )
• 55
• 56 retailPrice price
• 57
• 58
• 59 /
• 60 getManufact method
• 61 _at_return The name of the phone's
  manufacturer.
• 62 /
• 63
• 64 public String getManufact()

28

• 69 /
• 70 getModel method
• 71 _at_return The phone's model number.
• 72 /
• 73
• 74 public String getModel()
• 75
• 76 return model
• 77
• 78
• 79 /
• 80 getretailPrice method
• 81 _at_return The phone's retail price.
• 82 /
• 83
• 84 public double getRetailPrice()
• 85
• 86 return retailPrice

29

• Code Listing 6-13 (CellPhoneTest.java)
• 1 import java.util.Scanner
• 2
• 3 /
• 4 This program runs a simple test
• 5 of the CellPhone class.
• 6 /
• 7
• 8 public class CellPhoneTest
• 9
• 10 public static void main(String args)
• 11
• 12 String testMan // To hold a
  manufacturer
• 13 String testMod // To hold a
  model number
• 14 double testPrice // To hold a
  price
• 15
• 16 // Create a Scanner object for keyboard
  input.
• 17 Scanner keyboard new Scanner(System.in)
• 18

30

• 23 // Get the model number.
• 24 System.out.print("Enter the model number
  ")
• 25 testMod keyboard.nextLine()
• 26
• 27 // Get the retail price.
• 28 System.out.print("Enter the retail price
  ")
• testPrice keyboard.nextDouble()
  
• 30 // Create an instance of the
  CellPhone class,
• 31
• 32
• 34 CellPhone phone new CellPhone( testMan,
  testMod, testPrice )
• 35
• 36 // Get the data from the phone and display
  it.
• 37 System.out.println()
• 38 System.out.println("Here is the data that
  you provided")
• 39 System.out.println("Manufacturer "
  phone.getManufact())
• 40 System.out.println("Model number "
  phone.getModel())

31

• Program Output with Example Input Shown in Bold
• Enter the manufacturer Acme Electronics Enter
  
• Enter the model number M1000 Enter
• Enter the retail price 199.99 Enter
• Here is the data that you provided
• Manufacturer Acme Electronics
• Model number M1000
• Retail price 199.99

32

• Code Listing 6-14 (Die.java)
• 1 import java.util.Random
• 2
• 3 /
• 4 The Die class simulates a six-sided die.
• 5 /
• 6
• 7 public class Die
• 8
• 9 private int sides // Number
  of sides
• 10 private int value // The
  die's value
• 11
• 12 /
• 13 The constructor performs an initial
• 14 roll of the die.
• 15 _at_param numSides The number of sides for this
  die.
• 16 /
• 17
• 18 public Die( int numSides )

33

• 24 /
• 25 The roll method simulates the rolling of
• 26 the die.
• 27 /
• 28
• 29 public void roll()
• 30
• 31 // Create a Random object.
• 32 Random rand new Random()
• 33
• 34 // Get a random value for the die.
• 35 value rand.nextInt(sides) 1 //
  What is value?
• 36
• 37
• 38 /
• 39 getSides method
• 40 _at_return The number of sides for this die.
• 41 /

34

• 47
• 48 /
• 49 getValue method
• 50 _at_return The value of the die.
• 51 /
• 52
• 53 public int getValue()
• 54
• 55 return value
• 56
• 57 End Class

35

• Code Listing 6-15 (DiceDemo.java)
• 1 /
• 2 This program simulates the rolling of dice.
• 3 /
• 4
• 5 public class DiceDemo
• 6
• 7 public static void main(String args)
• 8
• 9 final int DIE1_SIDES 6 //
  Number of sides for die 1
• 10 final int DIE2_SIDES 12 // Number of
  sides for die 2
• 11 final int MAX_ROLLS 5 //
  Number of times to roll
• 12
• 13 // Create two instances of the Die class.
• 14 Die die1 new Die(DIE1_SIDES)
• 15 Die die2 new Die(DIE2_SIDES)
• 16
• 17 // Display the initial state of the dice.
• 18 System.out.println("This simulates the
  rolling of a "

36

• 24
• // Roll the dice five times.
• 26 System.out.println("Rolling the dice "
  MAX_ROLLS " times.")
• 27
• 28 for (int i 0 i lt MAX_ROLLS i)
• 29
• 30 // Roll the dice.
• 31 die1.roll()
• 32 die2.roll()
• 33
• 34 // Display the values of the dice.
• 35 System.out.println( die1.getValue() " "
  die2.getValue() )
• 36
• 37
• 38
• Program Output
• This simulates the rolling of a 6 sided die and a
  12 sided die.

37

• Code Listing 6-16 (DieArgument.java)
• 1 /
• 2 This program rolls a 6-sided die and
• 3 a 20-sided die.
• 4 /
• 5
• 6 public class DieArgument
• 7
• 8 public static void main(String args)
• 9
• 10 final int SIX_SIDES 6
• 11 final int TWENTY_SIDES 20
• 12
• 13
• 14 Die sixDie new Die(SIX_SIDES)
• 15
• 16
• 17 Die twentyDie new Die(TWENTY_SIDES)
• 18

38

• 23
• 24 /
• 25 This method simulates a die roll, displaying
• 26 the die's number of sides and value.
• 27 _at_param d The Die object to roll.
• 28 /
• 29
• 30 public static void rollDie(Die d) //
  Receiving the Reference Argument
• 31
• 32 // Display the number of sides.
• 33 System.out.println("Rolling a "
  d.getSides()
• 34 " sided die.")
• 35
• 36 // Roll the die.
• 37 d.roll()
• 38
• 39 // Display the die's value.
• 40 System.out.println("The die's value "
  d.getValue())
• 41

39

• Code Listing 6-17 (Dealer.java)
• 1 /
• 2 Dealer class for the game of Cho-Han( Uses Die
  class )
• 3 /
• 4
• 5 public class Dealer
• 6
• 7 private int die1Value // The value of die 1
• 8 private int die2Value // The value of die 2
• 9
• 10 /
• 11 Constructor
• 12 /
• 13
• 14 public Dealer()
• 15
• 16 die1Value 0
• 17 die2Value 0
• 18

40

• 24
• 25 public void rollDice()
• 26
• 27 final int SIDES 6 // Number of sides for
  the dice
• 28
• 29 // Create the two dice. (This also rolls
  them.)
• 30 Die die1 new Die(SIDES)
• 31 Die die2 new Die(SIDES)
• 32
• 33
• 34 die1Value die1.getValue() // Where is
  memory for die1Value
• 35 die2Value die2.getValue() // and
  die2Value allocated?
• 36
• 37
• 38 /
• 39 The getChoOrHan method returns the result of
• 40 the dice roll, Cho or Han.
• 41 _at_return Either "Cho (even)" or "Han (odd)"

41

• 47
• 48 // Get the sum of the dice.
• 49 int sum die1Value die2Value
• 50
• 51 // Determine even or odd.
• 52 if (sum 2 0)
• 53 result "Cho (even)"
• 54 else
• 55 result "Han (odd)"
• 56
• 57 // Return the result.
• 58 return result
• 59
• 60
• 61 /
• 62 The getDie1Value method returns the value of
• 63 die 1.
• 64 _at_return The die1Value field

42

• 67 public int getDie1Value()
• 68
• 69 return die1Value
• 70
• 71
• 72 /
• 73 The getDie2Value method returns the value of
• 74 die 2.
• 75 _at_return The die2Value field
• 76 /
• 77
• 78 public int getDie2Value()
• 79
• 80 return die2Value
• 81
• 82

43

• Code Listing 6-18 (Player.java)
• 1 import java.util.Random
• 2
• 3 /
• 4 Player class for the game of Cho-Han
• 5 /
• 6
• 7 public class Player
• 8
• 9 private String name // The player's name
• 10 private String guess // The player's guess
• 11 private int points // The player's
  points
• 12
• 13 /
• 14 Constructor
• 15 _at_param playerName The player's name.
• 16 /
• 17
• 18 public Player(String playerName)

44

• 24
• 25 /
• 26 The makeGuess method causes the player to
  guess
• 27 either "Cho (even)" or "Han (odd)".
• 28 /
• 29
• 30 public void makeGuess()
• 31
• 33 Random rand new Random()
• 34
• 36 int guessNumber rand.nextInt(2)
• 37
• 38 // Convert the random number to a guess of
• // either "Cho (even)" or "Han (odd)".
• 40 if (guessNumber 0)
• 41 guess "Cho (even)"
• 42 else
• 43 guess "Han (odd)"

45

• 46 /
• 47 The addPoints method adds a specified number
  of
• 48 points to the player's current balance.
• 49 _at_newPoints The points to add.
• 50 /
• 51
• 52 public void addPoints(int newPoints)
• 53
• 54 points newPoints
• 55
• 56
• 57 /
• 58 The getName method returns the player's
  name.
• 59 _at_return The value of the name field.
• 60 /
• 61
• 62 public String getName()
• 63

46

• 67 /
• 68 The getGuess method returns the player's
  guess.
• 69 _at_return The value of the guess field.
• 70 /
• 71
• 72 public String getGuess()
• 73
• 74 return guess
• 75
• 76
• 77 /
• 78 The getPoints method returns the player's
  points
• 79 _at_return The value of the points field.
• 80 /
• 81
• 82 public int getPoints()
• 83
• 84 return points

47

• Code Listing 6-19 (ChoHan.java)
• 1 import java.util.Scanner
• 2
• 3 public class ChoHan
• 4
• 5 public static void main(String args)
• 6
• 7 final int MAX_ROUNDS 5 //
  Number of rounds
• 8 String player1Name // First
  player's name
• 9 String player2Name // Second
  player's name
• 10
• 11
• 12 Scanner keyboard new Scanner(System.in)
• 13
• 15 System.out.print("Enter the first player's
  name ")
• player1Name keyboard.nextLine()
• 17 System.out.print("Enter the second player's
  name ")
• 18 player2Name keyboard.nextLine()

48

• 23 // Create the two players.
• 24 Player player1 new Player(player1Name)
• 25 Player player2 new Player(player2Name)
• 26
• 27 // Play the rounds.
• 28 for (int round 0 round lt MAX_ROUNDS
  round)
• 29
• 30 System.out.println("------------------------
  ----")
• 31 System.out.printf("Now playing round
  d.\n", round 1)
• 32
• 33 // Roll the dice.
• 34 dealer.rollDice()
• 35
• 36 // The players make their guesses.
• 37 player1.makeGuess()
• 38 player2.makeGuess()
• 39
• 40 // Determine the winner of this round.

49

• 46 End Main
• 47
• 48 /
• 49 The roundResults method determines the
  results of
• 50 the current round.
• 51 _at_param dealer The Dealer object
• 52 _at_param player1 Player 1 object
• 53 _at_param player2 Player 2 object
• 54 /
• 55
• 56 public static void roundResults( Dealer
  dealer, Player player1,
• 57 Player player2 )
• 58
• 59 // Show the dice values.
• 60 System.out.printf("The dealer rolled d and
  d.\n",
• 61 dealer.getDie1Value(),
  dealer.getDie2Value())
• 62 System.out.printf("Result s\n",
  dealer.getChoOrHan() )
• 63
• 64 // Check each player's guess and award
  points.

50

• 68
• 69 /
• 70 The checkGuess method checks a player's
  guess against
• 71 the dealer's result.
• 72 _at_param player The Player object to check.
• 73 _at_param dealer The Dealer object.
• 74 /
• 75
• 76 public static void checkGuess( Player player,
  Dealer dealer )
• 77
• 78 final int POINTS_TO_ADD 1
  // Points to award winner
• 79 String guess player.getGuess()
  // Player's guess
• 80 String choHanResult dealer.getChoOrHan()
  // Cho or Han
• 81
• 82 // Display the player's guess.
• 83 System.out.printf("The player s guessed
  s.\n",
• 84 player.getName(), player.getGuess())
• 85
• // Award points if the player guessed correctly.

51

• 88
• 89 player.addPoints(POINTS_TO_ADD)
• 90 System.out.printf("Awarding d point(s) to
  s.\n",
• 91 POINTS_TO_ADD, player.getName() )
• 92
• 93 // End checkGuess
• 94
• 95 /
• 96 The displayGrandWinner method displays the
  game's grand winner.
• 97 _at_param player1 Player 1
• 98 _at_param player2 Player 2
• 99 /
• 100
• 101 public static void displayGrandWinner(
  Player player1, Player player2 )
• 102
• 103 System.out.println("-------------------------
  ---")
• 104 System.out.println("Game over. Here are the
  results")
• 105 System.out.printf("s d points.\n",
  player1.getName(),

52

• 110 if ( player1.getPoints() gt
  player2.getPoints() )
• 111 System.out.println( player1.getName() "
  is the grand winner!")
• 112 else if ( player2.getPoints() gt
  player1.getPoints() )
• 113 System.out.println( player2.getName() "
  is the grand winner!")
• 114 else
• 115 System.out.println("Both players are
  tied!")
• 116
• 117
• Program Output
• Enter the first player's name Chelsea Enter
• Enter the second player's name Chris Enter
• ----------------------------
• Now playing round 1.
• The dealer rolled 3 and 6.
• Result Han (odd)
• The player Chelsea guessed Han (odd).

53

• ----------------------------
• Now playing round 2.
• The dealer rolled 4 and 5.
• Result Han (odd)
• The player Chelsea guessed Cho (even).
• The player Chris guessed Cho (even).
• ----------------------------
• Now playing round 3.
• The dealer rolled 5 and 6.
• Result Han (odd)
• The player Chelsea guessed Cho (even).
• The player Chris guessed Han (odd).
• Awarding 1 point(s) to Chris.
• ----------------------------
• Now playing round 4.
• The dealer rolled 1 and 6.
• Result Han (odd)
• The player Chelsea guessed Cho (even).
• The player Chris guessed Cho (even).

54

• Now playing round 5.
• The dealer rolled 6 and 6.
• Result Cho (even)
• The player Chelsea guessed Han (odd).
• The player Chris guessed Cho (even).
• Awarding 1 point(s) to Chris.
• ----------------------------
• Game over. Here are the results
• Chelsea 1 points.
• Chris 3 points.
• Chris is the grand winner!

55

• Code Listing 6-20 (BankAccount.java)
• 1 /
• 2 The BankAccount class simulates a bank
  account.
• 3 /
• 4
• 5 public class BankAccount
• 6
• 7 private double balance // Account
  balance Data field( Instance Variable )
• 8
• 9 /
• 10 This constructor - 1 sets the starting
  balance
• 11 at 0.0.
• 12 /
• 13
• 14 public BankAccount()
• 15
• 16 balance 0.0
• 17
• 18

56

• 24
• 25 public BankAccount( double startBalance )
• 26
• 27 balance startBalance
• 28
• 29
• 30 /
• 31 This constructor 3 sets the starting
  balance
• 32 to the value in the String argument.
• 33 _at_param str The starting balance, as a
  String.
• 34 /
• 35
• 36 public BankAccount( String str )
• 37
• 38 balance Double.parseDouble(str)
• 39
• 40
• 41 /

57

• 47
• 48 public void deposit( double amount )
• 49
• 50 balance amount
• 51
• 52
• 53 /
• 54 The deposit method 2 makes a deposit into
• 55 the account.
• 56 _at_param str The amount to add to the
• 57 balance field, as a String.
• 58 /
• 59
• 60 public void deposit(String str)
• 61
• 62 balance Double.parseDouble(str)
• 63
• 64

58

• 69 the balance field.
• 70 /
• 71
• 72 public void withdraw( double amount )
• 73
• 74 balance - amount
• 75
• 76
• 77 /
• 78 The withdraw method 2 withdraws an amount
• 79 from the account.
• 80 _at_param str The amount to subtract from
• 81 the balance field, as a String.
• 82 /
• 83
• 84 public void withdraw( String str )
• 85
• 86 balance - Double.parseDouble(str)

59

• 91 _at_param b The value to store in the balance
  field.
• 92 /
• 93
• 94 public void setBalance(double b)
• 95
• 96 balance b
• 97
• 98
• 99 /
• 100 The setBalance method 2 sets the account
  balance.
• 101 _at_param str The value, as a String, to store
  in
• 102 the balance field.
• 103 /
• 104
• 105 public void setBalance(String str)
• 106
• 107 balance Double.parseDouble(str)
• 108

60

• 110 /
• 111 The getBalance method returns the
• 112 account balance.
• 113 _at_return The value in the balance field.
• 114 /
• 115
• 116 public double getBalance()
• 117
• 118 return balance
• 119
• 120

61

• Code Listing 6-21 (AccountTest.java)
• 1 import javax.swing.JOptionPane // For the
  JOptionPane class
• 2 import java.text.DecimalFormat // For the
  DecimalFormat class
• 3
• 4 /
• 5 This program demonstrates the BankAccount
  class.
• 6 /
• 7
• 8 public class AccountTest
• 9
• 10 public static void main(String args)
• 11
• 12 String input
• 13
• 14 // Create a DecimalFormat object for
  displaying dollars.
• 15 DecimalFormat dollar new
  DecimalFormat(",.00")
• 16
• 17 // Get the starting balance.
• 18 input JOptionPane.showInputDialog("What is
  your "

62

• 23
• 24 // Get the amount of pay.
• 25 input JOptionPane.showInputDialog("How
  much were "
• 26 "you paid this month? ")
• 27
• 28 // Deposit the user's pay into the account.
• 29 account.deposit(input)
• 30
• 31 // Display the new balance.
• 32 JOptionPane.showMessageDialog(null,
• 33 "Your pay has been deposited.\n"
• 34 "Your current balance is "
• 35 dollar.format( account.getBalance()) )
• 36
• 37 // Withdraw some cash from the account.
• 38 input JOptionPane.showInputDialog("How
  much would "
• 39 "you like to withdraw? ")
• account.withdraw(input)

63

• (Continued) Code Listing 6-21 (AccountTest.java)
• 46
• 47 System.exit(0)
• 48
• 49