Starting Out with Java:
From Control Structures
through Objects
5th edition
By Tony Gaddis
Source Code: Chapter 6
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
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16
// Create a Scanner object for keyboard input.
17
Scanner keyboard = new Scanner(System.in);
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// Create a Random object to generate random numbers.
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Random rand = new Random();
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PrintWriter outputFile = new PrintWriter("numbers.txt");
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// Get the number of random numbers to write.
System.out.print("How many random numbers should I write? ");
maxNumbers = keyboard.nextInt();
// Write the random numbers to the file.
for (int count = 0; count < maxNumbers; count++)
{
number = rand.nextInt();
// Write the random integer to the file.
outputFile.println(number);
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42 }
43 }
}
// Close the file.
outputFile.close();
System.out.println("Done");
Program Output with Example Input Shown in Bold
How many random numbers should I write? 10 [ Enter]
Done
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
@param len The value to store in length.
15
*/
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public void setLength( double len )
18
{
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length = len;
20
}
21 }
Code Listing 6-3 (LengthDemo.java)
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/**
This program demonstrates the Rectangle class's
setLength method.
*/
public class LengthDemo
{
public static void main(String[] args)
{
// Create a Rectangle object.
Rectangle box = new Rectangle(); // Constructor method?
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// Call the box object's setLength method.
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box.setLength(10.0);
System.out.println("Sending the value 10.0 " +
"to the setLength method.");
(Continued)
20
21 // 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.
Code Listing 6-4 (Rectangle.java)
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/**
Rectangle class, phase 2
Under construction!
*/
public class Rectangle
{
private double length;
private double width;
/**
The setLength method stores a value in the
length field.
@param len The value to store in length.
*/
public void setLength( double len )
{
length = len;
}
(Continued)
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32 }
/**
The setWidth method stores a value in the
width field.
@param w The value to store in width.
*/
public void setWidth(double w)
{
width = w;
}
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
/**
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The setLength method stores a value in the
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length field.
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@param len The value to store in length.
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*/
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public void setLength(double len)
18
{
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length = len;
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}
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(Continued)
22 /**
23
The setWidth method stores a value in the
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width field.
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@param w The value to store in width.
26 */
27
28 public void setWidth(double w)
29 {
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width = w;
31 }
32
33 /**
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The getLength method returns a Rectangle
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object's length.
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@return The value in the length field.
37 */
38
39 public double getLength()
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{
return length;
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}
(Continued)
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54 }
/**
The getWidth method returns a Rectangle
object's width.
@return The value in the width field.
*/
public double getWidth()
{
return width;
}
Code Listing 6-6 (LengthWidthDemo.java)
1 /**
This program demonstrates the Rectangle class's
3 setLength, setWidth, getLength, and getWidth methods.
2
4 */
5
6 public
7 {
class LengthWidthDemo
8 public static void main(String[] args)
9 {
10
// Create a Rectangle object.
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Rectangle box = new Rectangle();
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// Call the object's setLength method, passing 10.0
// as an argument.
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box.setLength(10.0);
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// Call the object's setWidth method, passing 20.0
// as an argument.
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box.setWidth(20.0);
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(Continued)
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// Display the object's length and width.
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System.out.println("The box's length is " +
box.getLength());
System.out.println("The box's width is " +
25
26 }
27 }
Program Output
The box's length is 10.0
The box's width is 20.0
box.getWidth());
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
@param len The value to store in length.
15 */
16
17 public void setLength( double len )
18 {
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length = len;
20 }
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(Continued)
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/**
The setWidth method stores a value in the
width field.
@param w The value to store in width.
*/
public void setWidth( double w )
{
width = w;
}
/**
The getLength method returns a Rectangle
object's length.
@return The value in the length field.
*/
public double getLength()
{
return length;
}
(Continued)
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65 }
/**
The getWidth method returns a Rectangle
object's width.
@return The value in the width field.
*/
public double getWidth()
{
return width;
}
/**
The getArea method returns a Rectangle
object's area.
@return The product of length times width.
*/
public double getArea()
{
return length
}
* width;
// What is Stale data?
Code Listing 6-8 (RectangleDemo.java)
1 /**
2
This program demonstrates the Rectangle
3
setLength, setWidth, getLength, getWidth, and
4
getArea methods.
5 */
6
7 public class RectangleDemo
8 {
9
public static void main(String[] args)
10 {
class's
11 // Create a Rectangle object.
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Rectangle box = new Rectangle();
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box.setLength(10.0);
box.setWidth(20.0);
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17
18 // Display the length.
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System.out.println("The box's length is " +
box.getLength());
(Continued)
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// Display the width.
System.out.println("The box's width is " +
box.getWidth());
// Display the area.
27
System.out.println("The box's area is " +
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box.getArea());
29 }
30 }
Program Output
The box's length is 10.0
The box's width is 20.0
The box's area is 200.0
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
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double totalArea;
// The total area
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String input;
// To hold user input
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// Create three Rectangle objects.
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Rectangle kitchen = new Rectangle();
Rectangle bedroom = new Rectangle();
Rectangle den = new Rectangle();
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input = JOptionPane.showInputDialog("What is the " +
"kitchen's length?");
number = Double.parseDouble(input);
kitchen.setLength(number);
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input = JOptionPane.showInputDialog("What is the " +
"kitchen's width?");
number = Double.parseDouble(input);
kitchen.setWidth(number);
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// Get and store the dimensions of the bedroom.
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input = JOptionPane.showInputDialog("What is the " +
"bedroom's length?");
number = Double.parseDouble(input);
bedroom.setLength(number);
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input = JOptionPane.showInputDialog("What is the " +
"bedroom's width?");
number = Double.parseDouble(input);
bedroom.setWidth(number);
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(Continued)
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input = JOptionPane.showInputDialog("What is the " +
"den's length?");
number = Double.parseDouble(input);
den.setLength(number);
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input = JOptionPane.showInputDialog("What is the " +
"den's width?");
number = Double.parseDouble(input);
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den.setWidth(number);
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totalArea = kitchen.getArea() + bedroom.getArea()
+ den.getArea();
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JOptionPane.showMessageDialog(null, " + "The total area” +
"of the rooms is " + totalArea);
System.exit(0);
}
Code Listing 6-10 (Rectangle.java)
1 /**
2
Rectangle class,
3 */
4
phase 5
5 public class Rectangle
6 {
7
private double length;
8
private double width;
9
10
/**
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Constructor
@param len The length of the rectangle.
@param w The width of the rectangle.
*/
public Rectangle( double len, double w )
{
length = len;
width = w;
}
. . . The
remainder of the class has not changed, and is not shown.
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
11
// 15.0 as arguments to the constructor.
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Rectangle box = new Rectangle( 5.0, 15.0 );
// Display the length.
System.out.println("The box's length is " +
box.getLength());
// Display the width.
System.out.println("The box's width is " +
box.getWidth());
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(Continued)
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// Display the area.
System.out.println("The box's area is " +
24
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
box.getArea());
Code Listing 6-12 (CellPhone.java)
1 /**
2 The CellPhone class holds data about a cell phone.
3 */
4
5 public class
6 {
7 // Fields
8
9
CellPhone
private String manufact;
private String model;
private double retailPrice;
10
11
12 /**
13
Constructor
14
@param man The phone's manufacturer.
15
@param mod The phone's model number.
16
@param price The phone's retail price.
17 */
18
19 public
20 {
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// Manufacturer
// Model
// Retail
price
CellPhone( String man, String mod, double price )
manufact = man;
model = mod;
retailPrice = price;
(Continued)
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}
/**
The setManufact method sets the phone's
manufacturer name.
@param man The phone's manufacturer.
*/
public void setManufact( String man )
{
manufact = man;
}
/**
The setMod method sets the phone's
model number.
@param mod The phone's model number.
*/
public void setMod( String mod )
{
model = mod;
}
(Continued)
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/**
The setRetailPrice method sets the phone's
retail price.
@param price The phone's retail price.
*/
public void setRetailPrice( double price )
{
retailPrice = price;
}
/**
getManufact method
@return The name of the phone's manufacturer.
*/
public String getManufact()
{
return manufact;
}
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(Continued)
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/**
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88 }
getModel method
@return The phone's model number.
*/
public String getModel()
{
return model;
}
/**
getretailPrice method
@return The phone's retail price.
*/
public double getRetailPrice()
{
return retailPrice;
}
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
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testMod;
double testPrice;
String
// To hold a model number
// To hold a price
// Create a Scanner object for keyboard input.
Scanner keyboard = new Scanner(System.in);
// Get the manufacturer name.
System.out.print("Enter the manufacturer: ");
testMan = keyboard.nextLine();
(Continued)
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// Get the model number.
System.out.print("Enter the model number: ");
testMod = keyboard.nextLine();
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// Create an instance of the CellPhone class,
// Get the retail price.
System.out.print("Enter the retail price: ");
testPrice = keyboard.nextDouble();
CellPhone phone =
new CellPhone( testMan, testMod, testPrice );
// Get the data from the phone and display it.
System.out.println();
System.out.println("Here is the data that you provided:");
System.out.println("Manufacturer: " + phone getManufact());
.
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System.out.println("Model number: " + phone.getModel());
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42
43 }
System.out.println("Retail price: " + phone.getRetailPrice());
}
(Continued)
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
Code Listing 6-14 (Die.java)
1 import java.util.Random;
2
3 /**
4 The Die class simulates
5 */
6
7 public class Die
{
9 private int sides;
10 private int value;
a die of varying sizes.
8
// Number of sides
// The die's value
11
12 /**
13
The constructor performs an initial
14
roll of the die.
15
@param numSides The number of sides for this die.
16 */
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public Die( int numSides )
{
sides = numSides;
roll();
// What are we calling?
}
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(Continued)
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/**
The roll method simulates the rolling of
the die.
*/
public void roll()
{
// Create a Random object.
Random rand = new Random();
// Get a random value for the die.
value = rand.nextInt(sides)
+ 1;
// What is value?
}
/**
getSides method
@return The number of sides for this die.
*/
public int getSides()
{
return sides;
// What is sides?
}
(Continued)
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48 /**
49
getValue method
50
@return The value of the die.
51 */
52
53 public
54 {
55
int getValue()
return value;
56 }
57 }
End Class
Code Listing 6-15 (DiceDemo.java)
1 /**
2 This
3 */
4
program simulates the rolling of dice.
5 public
6 {
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class DiceDemo
public static void main(String[] args)
{
final int DIE1_SIDES
= 6;
final int DIE2_SIDES = 12;
final int MAX_ROLLS = 5;
// Number of sides for die #1
// Number of sides for die #2
// Number of times to roll
Die die1 = new Die(DIE1_SIDES);
Die die2 = new Die(DIE2_SIDES);
// Display the initial state of the dice.
System.out.println("This
simulates the rolling of a " +
DIE1_SIDES + " sided die and a " +
DIE2_SIDES + " sided die.");
System.out.println("Initial
value of the dice:");
// ?
System.out.println( die1.getValue() + " " + die2.getValue() );
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// Roll
the dice five times.
System.out.println("Rolling the dice " + MAX_ROLLS + " times.");
for (int i = 0; i < MAX_ROLLS; i++)
{
// Roll the dice.
die1.roll();
die2.roll();
// Display the values of the dice.
System.out.println( die1.getValue()
+ " " + die2.getValue() );
36
}
37
} // End main
38 } // End Class
Program Output
This simulates the rolling of a 6 sided die and a 12 sided die.
Initial value of the dice:
2 7
Rolling the dice 5 times.
3 5
5 2
2 1
4 1
Code Listing 6-16 (DieArgument.java)
1 /**
2
This program rolls a 6-sided die and
3
a 20-sided die. Client of Die.
4 */
5
6 public
7 {
8
9
10
11
12
13
class DieArgument
main
public static void
(String[] args)
{
final int SIX_SIDES = 6;
final int TWENTY_SIDES = 20;
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Die sixDie = new Die(SIX_SIDES);
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Die twentyDie = new Die(TWENTY_SIDES);
19
// Roll the dice.
20
rollDie(sixDie);
rollDie(twentyDie);
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22
// What type of method?
// Passing a Reference as an Argument
}
(Continued)
23
24 /**
25
This method simulates a die roll, displaying
26
the die's number of sides and value.
27
@param d The Die object to roll.
28 */
29
30 public static void rollDie(Die
31 {
32
// Display the number of sides.
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39
40
41 }
42 }
d)
//
Receiving the Reference Argument
.getSides() +
System.out.println("Rolling a " + d
" sided die.");
// Roll the die.
d.roll();
// Display the die's value.
.getValue());
System.out.println("The die's value: " + d
Program Output
Rolling a 6 sided die.
The die's value: 3
Rolling a 20 sided die.
The die's value: 19
Code Listing 6-17 (Dealer.java)
1 /**
2 Dealer class for the game of Cho-Han( Uses Die class )
3 */
4
5 public
6 {
7
class Dealer
private int die1Value;
private int die2Value;
8
9
10 /**
11
Constructor
12 */
13
14 public
15 {
16
17
18 }
19
20 /**
21
22
23 */
// The
value of die #1
// The
value of die #2
Dealer()
die1Value = 0;
die2Value = 0;
The rollDice
their values.
method rolls the dice and saves
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public void rollDice()
{
final int SIDES = 6;
// Number of sides for the dice
// Create the two dice. (This also rolls them.)
Die die1 = new Die(SIDES);
Die die2 = new Die(SIDES);
die1Value = die1.getValue(); // Where is memory for die1Value
die2Value = die2.getValue(); // and die2Value allocated?
}
/**
The getChoOrHan method returns the result of
the dice roll, Cho or Han.
@return Either "Cho (even)" or "Han (odd)"
*/
public String getChoOrHan()
{
String result; // To hold the result
(Continued)
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// Get the sum of the dice.
int sum = die1Value + die2Value;
// Determine even or odd.
if (sum % 2 == 0)
result = "Cho (even)";
else
result = "Han (odd)";
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// Return the result.
return result;
}
/**
The getDie1Value method returns the value of
die #1.
@return The die1Value field
*/
67
public int getDie1Value()
68
{
69
return die1Value;
70
}
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/**
73
The getDie2Value method returns the value of
74
die #2.
75
@return The die2Value field
76
*/
77
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public int getDie2Value()
79
{
80
return die2Value;
81
}
82 }
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
10 private String guess;
// The player's
11 private int
points; // The player's
12
13 /**
14
Constructor
15
@param playerName The player's name.
16 */
17
18 public Player(String playerName)
19 {
20
name = playerName;
21
guess = "";
22
points = 0;
23 }
name
guess
points
(Continued)
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/**
The makeGuess method causes the player to guess
either "Cho (even)" or "Han (odd)".
*/
public void makeGuess()
{
Random rand = new Random();
int guessNumber = rand.nextInt(2);
// Convert the random number to a guess of
// either "Cho (even)" or "Han (odd)".
40
if (guessNumber == 0)
41
guess = "Cho (even)";
42 else
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guess = "Han (odd)";
44 }
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/**
The addPoints method adds a specified number of
points to the player's current balance.
@newPoints The points to add.
*/
public void addPoints(int newPoints)
{
points += newPoints;
}
/**
The getName method returns the player's name.
@return The value of the name field.
*/
public String getName()
{
return name;
}
(Continued)
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86 }
/**
The getGuess method returns the player's guess.
@return The value of the guess field.
*/
public String getGuess()
{
return guess;
}
/**
The getPoints method returns the player's points
@return The value of the points field.
*/
public int getPoints()
{
return points;
}
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);
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15
System.out.print("Enter the first player's name: ");
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player1Name = keyboard.nextLine();
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System.out.print("Enter the second player's name: ");
player2Name = keyboard.nextLine();
// Create the dealer.
Dealer dealer = new Dealer();
(Continued)
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36
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// Create the two players.
Player player1 = new Player(player1Name);
Player player2 = new Player(player2Name);
// Play the rounds.
for (int round = 0; round < MAX_ROUNDS; round++)
{
System.out.println("----------------------------");
System.out.printf("Now playing round %d.\n", round + 1);
// Roll the dice.
dealer.rollDice();
// The players make their guesses.
player1.makeGuess();
player2.makeGuess();
// Determine the winner of this round.
roundResults( dealer, player1, player2 );
41
42
43
}
44
// Display the grand winner.
45
displayGrandWinner( player1, player2 );
46 } // End Main
47
48 /**
49
The roundResults method determines the results of
50
the current round.
51
@param dealer The Dealer object
52
@param player1 Player #1 object
53
@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
62
63
64
65
66
67 }
dealer.getDie1Value(), dealer.getDie2Value());
System.out.printf("Result: %s\n", dealer.getChoOrHan() );
// Check each player's guess and award points.
checkGuess( player1, dealer );
checkGuess( player2, dealer );
(Continued)
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77
78
/**
The checkGuess method checks a player's guess against
the dealer's result.
@param player The Player object to check.
@param dealer The Dealer object.
*/
public static void checkGuess( Player player, Dealer dealer )
{
final int POINTS_TO_ADD = 1;
// Points to award winner
79
String guess = player.getGuess();
// Player's guess
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85
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String choHanResult = dealer.getChoOrHan();
// Cho or Han
// Award points if the player guessed correctly.
87
if (guess.equalsIgnoreCase( choHanResult) )
// Display the player's guess.
System.out.printf("The player %s guessed %s.\n",
player.getName(), player.getGuess());
(Continued)
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
@param player1 Player #1
98
@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(),
106
player1.getPoints());
107
System.out.printf("%s: %d points.\n", player2.getName(),
108
player2.getPoints());
109
(Continued)
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115
116 }
117 }
if ( player1.getPoints() > player2.getPoints() )
System.out.println( player1.getName() + " is the grand winner!");
else if ( player2.getPoints() > player1.getPoints() )
System.out.println( player2.getName() + " is the grand winner!");
else
System.out.println("Both players are tied!");
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).
Awarding 1 point(s) to Chelsea.
The player Chris guessed Han (odd).
Awarding 1 point(s) to Chris.
---------------------------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).
---------------------------(Continued)
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!
Code Listing 6-20 (BankAccount.java)
1 /**
2 The
3 */
4
BankAccount class simulates a bank account.
5 public
6 {
7
8
9
class BankAccount
private double balance;
// Account balance Data field( Instance Variable )
/**
10
11
12 */
13
This constructor - 1 sets the starting balance
at 0.0.
14 public BankAccount()
15 {
16
17 }
18
19 /**
balance = 0.0;
20
21
22
23 */
This constructor - 2 sets the starting balance
to the value passed as an argument.
@param startBalance The starting balance.
(Continued)
24
25 public BankAccount(
26 {
double startBalance )
27
28 }
29
30 /**
balance = startBalance;
31
32
33
34 */
35
This constructor – 3 sets the starting balance
to the value in the String argument.
@param str The starting balance, as a String.
36 public BankAccount(
37 {
String str )
38
39 }
40
41 /**
balance = Double.parseDouble(str);
42
43
44
45
46 */
The deposit method – 1 makes a deposit into
the account.
@param amount The amount to add to the
balance field.
(Continued)
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48
49
50
51
52
53
54
55
56
57
58
59
public void deposit( double amount )
{
balance += amount;
}
/**
The deposit method – 2 makes a deposit into
the account.
@param str The amount to add to the
balance field, as a String.
*/
60 public void deposit(String str)
61 {
62
balance += Double.parseDouble(str);
63 }
64
65 /**
66
The withdraw method - 1 withdraws an amount
67
from the account.
68
@param amount The amount to subtract from
(Continued)
69
70 */
71
the balance field.
72 public void withdraw(
73 {
double amount )
74
75 }
76
77 /**
balance -= amount;
78
79
80
81
82 */
83
The withdraw method – 2 withdraws an amount
from the account.
@param str The amount to subtract from
the balance field, as a String.
84 public void withdraw(
85 {
String str )
86
87 }
88
89 /**
balance -= Double.parseDouble(str);
90
The setBalance
method - 1 sets the account balance.
91
92 */
93
@param b The value to store in the balance field.
94 public void setBalance(double
95 {
b)
96
balance = b;
97 }
98
99 /**
100
The setBalance method – 2 sets the account balance.
101
@param str The value, as a String, to store in
102
the balance field.
103
*/
104
105
106
107
108
109
public void setBalance(String str)
{
balance = Double.parseDouble(str);
}
(Continued)
110
111
112
113
114
115
116
117
118
119
120 }
/**
The getBalance method returns the
account balance.
@return The value in the balance field.
*/
public double getBalance()
{
return balance;
}
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 " +
19
"account's starting balance?");
20
22
BankAccount account = new BankAccount(input);
(Continued)
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
// Get the amount of pay.
input = JOptionPane.showInputDialog("How much were " +
"you paid this month? ");
// Deposit the user's pay into the account.
account.deposit(input);
// Display the new balance.
JOptionPane.showMessageDialog(null,
"Your pay has been deposited.\n" +
"Your current balance is $ " +
.
.
dollar format( account getBalance()) );
// Withdraw some cash from the account.
input = JOptionPane.showInputDialog("How much would " +
"you like to withdraw? ");
account.withdraw(input);
41
42
43
44
45
// Display the new balance
JOptionPane.showMessageDialog(null,
"Now your balance is $" +
.
.
dollar format(account getBalance()) );
(Continued)
(Continued) Code Listing 6-21 (AccountTest.java)
46
47
48 }
49 }
System.exit(0);