Starting Out with Java:
From Control Structures
through Objects
5th edition
By Tony Gaddis
Source Code: Chapter 10
Code Listing 10-1 (GradedActivity.java)
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/**
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A class that holds a grade for a graded activity. General class that
will be “extended” later.
*/
public class GradedActivity
{
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private double score;
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public void setScore( double
{
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// Numeric score- Data Field
/**
The setScore method sets the score field.
@param s The value to store in score.
*/
s)
// Note: NO CONSTRUCTOR Explicit.
score = s;
}
/**
The getScore method returns the score.
@return The value stored in the score field.
*/
(Continued)
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public double getScore()
{
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return score;
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}
/**
The getGrade method returns a letter grade
determined from the score field.
@return The letter grade.
*/
public char getGrade()
{
char letterGrade;
if (score >= 90)
letterGrade = 'A';
else if (score >= 80)
letterGrade = 'B';
else if (score >= 70)
letterGrade = 'C';
(Continued)
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else if (score >= 60)
letterGrade = 'D';
else
letterGrade = 'F';
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51 }
52 }
return letterGrade;
Code Listing 10-2 (GradeDemo.java)
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import javax.swing.JOptionPane;
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double testScore;
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/**
This program demonstrates the GradedActivity
class. Not a sub class.
*/
public class GradeDemo
{
public static void main(String[] args)
{
String input;
// To hold input
// A test score
// Create a GradedActivity object.
GradedActivity grade = new GradedActivity();
//
Invokes What?
// Get a test score.
Input = JOptionPane.showInputDialog("Enter " +
"a numeric test score.");
testScore = Double.parseDouble(input);
(Continued)
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// Store the score in the grade object.
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grade setScore(testScore);
.
// Defined where?
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// Display the letter grade for the score.
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JOptionPane.showMessageDialog(null,
"The grade for that test is " +
grade.getGrade());
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32 }
33 }
System.exit(0);
Code Listing 10-3 (FinalExam.java)
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/**
2 This class determines the grade for a final exam. A sub class-inherits what?
3 Does not inherit?
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*/
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public class FinalExam extends GradedActivity
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{
private int
numQuestions;
private double pointsEach;
private int
numMissed;
// Number of questions
// Points for each question
// Questions missed
/**
The constructor sets the number of questions on the
exam and the number of questions missed.
@param questions The number of questions.
@param missed The number of questions missed.
*/
public FinalExam( int questions, int missed )
//
{
double numericScore;
// To hold a numeric score
// Set the
What is executed FIRST?
numQuestions and numMissed fields.
(Continued)
numQuestions = questions;
numMissed = missed;
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pointsEach = 100.0 / questions;
numericScore = 100.0 - (missed * pointsEach);
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// 3 IV’s are set.
// Call the inherited setScore method to
// set the numeric score.
setScore( numericScore );
//
Invokes what? Defined where? Why?
}
/**
The getPointsEach method returns the number of
points each question is worth.
@return The value in the pointsEach field.
*/
public double getPointsEach()
{
// Accessor
return pointsEach;
(Continued)
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}
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public int getNumMissed()
{
/**
The getNumMissed method returns the number of
questions missed.
@return The value in the numMissed field.
*/
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56 }
57 }
return numMissed;
// Accessor
Code Listing 10-4 (FinalExamDemo.java)
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import javax.swing.JOptionPane;
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This program demonstrates the
which extends the GradedActivity class.
*/
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/**
FinalExam class,
public class FinalExamDemo
{
public static void main(String[] args)
{
String input;
// To hold input
int questions;
// Number of questions
int missed;
// Number of questions missed
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// Get the number of questions on the exam.
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input = JOptionPane.showInputDialog("How many " +
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// Get the number of questions the student missed.
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input = JOptionPane.showInputDialog("How many " +
"questions are on the final exam?");
questions = Integer.parseInt(input);
(Continued)
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"questions did the student miss?");
missed = Integer.parseInt(input);
// Create a FinalExam object.
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FinalExam exam = new FinalExam(questions, missed);
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// Display the test results.
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JOptionPane.showMessageDialog(null,
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"Each question counts " + exam.getPointsEach() +
" points.\nThe exam score is " +
// Defined where?
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exam.getScore() + "\nThe exam grade is " +
exam.getGrade());
// Defined where?
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37 }
38 }
System.exit(0);
Code Listing 10-5 (SuperClass1.java)
1 public class SuperClass1
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{
/**
Constructor
*/
public SuperClass1()
{
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12 }
System.out.println("This is the " +
"superclass constructor.");
Code Listing 10-6 (SubClass1.java)
1 public class SubClass1 extends SuperClass1
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{
/**
Constructor
*/
public SubClass1()
{
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11 }
12 }
System.out.println("This is the " +
"subclass constructor.");
Code Listing 10-7 (ConstructorDemo1.java)
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/**
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This program demonstrates the order in which
superclass and subclass constructors are called.
*/
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public class ConstructorDemo1
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{
public static void
{
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11 }
12 }
main(String[] args)
SubClass1 obj = new SubClass1();
Program Output
This is the superclass constructor.
This is the subclass constructor.
Code Listing 10-8 (SuperClass2.java)
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public class SuperClass2
{
/**
Constructor #1 No-ARG
*/
public SuperClass2()
{
System.out.println("This is the superclass " +
"no-arg constructor.");
}
/**
Constructor #2 Accepts an Int
*/
17 public SuperClass2( int arg )
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19 {
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System.out.println ("The following argument was passed to the superclass " +
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"constructor: " + arg);
Code Listing 10-9 (SubClass2.java)
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public class SubClass2 extends SuperClass2
{
/**
Constructor
*/
public SubClass2()
{
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super(10);
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System.out.println("This is the " +
"subclass constructor.");
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12 }
13 }
// What if not included?
Code Listing 10-10 (ConstructorDemo2.java)
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/**
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This program demonstrates how a superclass
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constructor is called with the “super” key word.
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*/
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public class ConstructorDemo2
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public static void main(String[] args)
{
{
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11 }
12 }
SubClass2 obj = new SubClass2();
Program Output
The following argument was passed to the superclass constructor: 10
This is the subclass constructor.
Code Listing 10-11 (Cube.java)
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/**
This class holds data about a cube.
*/
5 public class Cube extends Rectangle
6 {
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private double height; // The cube's height
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/**
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The constructor sets the cube's length,
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width, and height.
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@param len The cube's length.
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@param w The cube's width.
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@param h The cube's height.
15 */
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public Cube(double len, double w, double h)
{
// Call the superclass constructor.
super(len, w);
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// Set the height.
// What if SUPER was not coded?
//
WHY?
What must you know to answer?
(Continued)
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height = h;
}
/**
The getHeight method returns the cube's height.
@return The value in the height field.
*/
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public double getHeight()
{
return height;
}
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public double getSurfaceArea()
{
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/**
The getSurfaceArea method calculates and
returns the cube's surface area.
@return The surface area of the cube.
*/
return getArea()
* 6;
// Where is getArea() defined?
(Continued)
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}
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public double getVolume()
{
/**
The getVolume method calculates and
returns the cube's volume.
@return The volume of the cube.
*/
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56 }
57 }
return getArea()
* height;
Code Listing 10-12 (CubeDemo.java)
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import java.util.Scanner;
/**
This program demonstrates passing arguments to a
superclass constructor.
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*/
public class CubeDemo
{
public static void main(String[] args)
{
double length;
// The cube's length
double width;
// The cube's width
double height;
// The cube's height
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter the following " +
"dimensions of a cube:");
System.out.print("Length: ");
(Continued)
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length = keyboard.nextDouble();
System.out.print("Width: ");
width = keyboard.nextDouble();
System.out.print("Height: ");
height = keyboard.nextDouble();
// Create
a cube object
Cube myCube =
new Cube(length, width, height); // Calls SubClass Constructor
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// Display
the cube's properties.
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System.out.println("Here are the cube's " +
"properties.");
System.out.println("Length: " +
myCube.getLength()); // Inherited
System.out.println("Width: " +
myCube.getWidth());
// Inherited
(Continued)
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System.out.println("Height: " +
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myCube.getHeight());
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System.out.println("Base Area: " +
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myCube.getArea());
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System.out.println("Surface Area: " +
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myCube.getSurfaceArea());
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System.out.println("Volume: " +
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myCube.getVolume());
53 }
54 }
Program Output with Example Input Shown in Bold
Enter the following dimensions of a cube:
Length: 10 [Enter]
Width: 15 [Enter]
Height: 12 [Enter]
Here are the cube's properties.
Length: 10.0
Width: 15.0
Height: 12.0
Base Area: 150.0
Surface Area: 900.0
Volume: 1800.0
// Local
// Inherited
// Local
//
Local
Code Listing 10-13 (CurvedActivity.java)
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/**
This class computes a curved grade. It extends
the GradedActivity class.
*/
6 public class CurvedActivity extends GradedActivity
7 {
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double rawScore;
// Unadjusted score
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double percentage;
// Curve percentage
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11 /**
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The constructor sets the curve percentage.
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@param percent The curve percentage.
14 */
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public CurvedActivity(double percent)
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{
percentage = percent;
rawScore = 0.0;
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// First Calls? - Why?
// Does it pass any arguments?
}
/**
(Continued)
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The setScore method overrides the superclass
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setScore method. This version accepts the
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unadjusted score as an argument. That score is
multiplied by the curve percentage and the
result is sent as an argument to the superclass's
setScore method.
@param s The unadjusted score.
*/
public void setScore(double s)
{
rawScore = s;
super.setScore(rawScore * percentage);
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}
/**
The getRawScore method returns the raw score.
@return The value in the rawScore field.
*/
public double getRawScore()
{
(Continued)
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return rawScore;
}
/**
The getPercentage method returns the curve
percentage.
@return The value in the percentage field.
*/
54 public double getPercentage()
55 {
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return percentage;
57 }
58 }
Code Listing 10-14 (CurvedActivityDemo.java)
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import java.util.Scanner;
/**
This program demonstrates the CurvedActivity
class,
which inherits from the GradedActivity class.
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*/
public class CurvedActivityDemo
{
public static void main(String[] args)
{
double score;
// Raw score
double curvePercent;
// Curve percentage
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter the student's " +
"raw numeric score: ");
score = keyboard.nextDouble();
(Continued)
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System.out.print("Enter the curve percentage: ");
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curvePercent = keyboard.nextDouble();
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CurvedActivity curvedExam = new CurvedActivity(curvePercent);
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curvedExam.setScore(score);
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// Display the raw score.
// Called?
// Called which method? Why?
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System.out.println("The raw score is " + curvedExam.getRawScore() +
" points.");
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System.out.println("The curved score is " + curvedExam.getScore());
// Display the curved score.
// Inherited.
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// Display the exam grade.
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System.out.println("The exam grade is " + curvedExam.getGrade());
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46 }
47 } // end class
// Inherited.
Program Output with Example Input Shown in Bold
Enter the student's raw numeric score:
Enter the curve percentage:
87 [Enter]
1.06 [Enter]
The raw score is 87.0 points.
The curved score is 92.22
The exam grade is A
Code Listing 10-15 (SuperClass3.java)
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public class SuperClass3
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{
/**
This method displays an int.
@param arg An int.
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*/
public void showValue( int arg )
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{
// Object?
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// Overridden in subclass
// Can this be called through a subclass
System.out.println("SUPERCLASS: " +
"The int argument was " + arg);
}
/**
This method displays a String.
@param arg A String.
Is showValue “overloaded in this class?
*/
public void showValue( String arg )
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{
System.out.println("SUPERCLASS: " +
"The String argument was " + arg);
Code Listing 10-16 (SubClass3.java)
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public class SubClass3 extends SuperClass3
{
/**
This method overrides one of the
superclass methods.
@param arg An int.
*/
public void showValue( int
arg )
// <-This May be called thru?
// <-add super.showvalue(arg);
//
AND What is impact?
10 {
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System.out.println("SUBCLASS: " +
"The int argument was " + arg);
}
/**
This method overloads the superclass
methods.
@param arg A double.
*/
public void showValue( double
{
arg )
// May be called thru?
(Continued)
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25 }
26 }
System.out.println("SUBCLASS: " +
"The double argument was " + arg);
Code Listing 10-17 (ShowValueDemo.java)
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/**
This program demonstrates the methods in the
SuperClass3 and SubClass3 classes.
*/
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public class ShowValueDemo
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public static void main(String[] args)
{
{
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SubClass3 myObject = new SubClass3();
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myObject.showValue( 10 );
// Pass an int.
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myObject.showValue( 1.2 );
// Pass a double.
THRU A SUBCLASS
// Pass a String.
OBJECT.
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myObject.showValue( "Hello“ );
16 }
17 }
Program Output
SUBCLASS: The int argument was 10
SUBCLASS: The double argument was 1.2
SUPERCLASS: The String argument was Hello
ALL 3 ARE CALLS
// How would you call
// Superclass method
// showvalue(int arg) ?
See pg. 648(earlier slide)
Code Listing 10-18 (GradedActivity2.java)
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/**
A class that holds a grade for a graded activity.
*/
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public class GradedActivity2
{
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protected double score;
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public void setScore(double
{
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// Numeric score
/**
The setScore method sets the score field.
@param s The value to store in score.
*/
s)
score = s;
}
/**
The getScore method returns the score.
@return The value stored in the score field.
*/
(Continued)
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public double getScore()
{
return
score;
}
/**
The getGrade method returns a letter grade
determined from the score field.
@return The letter grade.
*/
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public char getGrade()
{
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char letterGrade;
if (score >= 90)
letterGrade = 'A';
else if (score >= 80)
letterGrade = 'B';
else if (score >= 70)
letterGrade = 'C';
(Continued)
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else if (score >= 60)
letterGrade = 'D';
else
letterGrade = 'F';
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51 }
52 }
return letterGrade;
Code Listing 10-19 (FinalExam2.java)
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/**
This class determines the grade for a final exam.
The numeric score is rounded up to the next whole
number if its fractional part is .5 or greater.
*/
7 public class FinalExam2 extends GradedActivity2
8 {
9
private int
numQuestions;
// Number of questions
10 private double pointsEach;
// Points for each question
11 private int
numMissed;
// Number of questions missed
12
13 /**
14
The constructor sets the number of questions on the
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exam and the number of questions missed.
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@param questions The number of questions.
17
@param missed The number of questions missed.
18 */
19 //
Constructor Code
19 //----------------------------------------------------------------------------------------------------20 public FinalExam2( int questions, int missed )
21 {
22
double numericScore;
// To hold a numeric score
(Continued)
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// Set the numQuestions and numMissed fields.
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numQuestions = questions;
numMissed = missed;
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// Calculate the points for each question and
// the numeric score for this exam.
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pointsEach = 100.0 / questions;
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numericScore = 100.0 - (missed * pointsEach);
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// Call the inherited setScore method to
// set the numeric score.
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setScore( numericScore );
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// Inherited?
// Adjust the score.
adjustScore();
// Where is method defined?
} //--------------------------------------------------------------------------------------------------/**
The getPointsEach method returns the number of
points each question is worth.
@return The value in the pointsEach field.
(Continued)
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*/
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public double getPointsEach()
{
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public int getNumMissed()
{
return pointsEach;
}
/**
The getNumMissed method returns the number of
questions missed.
@return The value in the numMissed field.
*/
return numMissed;
}
/**
The adjustScore method adjusts a numeric score.
If score is within 0.5 points of the next whole
number, it rounds the score up.
(Continued)
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*/
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private void adjustScore()
// Called from constructor
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{
// Why is “score” directly available to this
// method?
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double fraction;
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// Get the fractional part of the score.
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fraction = score - (int) score;
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// If the fractional part is .5 or greater,
// round the score up to the next whole number.
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if (fraction >= 0.5)
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score = score + (1.0 - fraction);
80 }
81 } // end class
Code Listing 10-20 (ProtectedDemo.java)
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import javax.swing.JOptionPane;
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public class ProtectedDemo
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/**
This program demonstrates the FinalExam2 class,
which extends the GradedActivity2 class.
*/
{
public static void main(String[] args)
{
String input;
// To hold input
questions;
missed;
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int
// Number of questions
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Int
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input = JOptionPane.showInputDialog("How many " +
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questions = Integer.parseInt(input);
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input = JOptionPane.showInputDialog("How many " +
// Number of questions missed
"questions are on the final exam?");
(Continued)
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"questions did the student miss?");
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missed = Integer.parseInt(input);
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// Create a FinalExam object.
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FinalExam2 exam = new FinalExam2( questions, missed );
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// Display the test results.
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JOptionPane.showMessageDialog(null,
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"Each question counts " + exam.getPointsEach() +
" points.\nThe exam score is " +
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exam.getScore() + "\nThe exam grade is " +
exam.getGrade());
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37 }
38 }
System.exit(0);
Code Listing 10-21 (PassFailActivity.java)
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/**
This class holds a numeric score and determines
whether the score is passing or failing.
*/
6 public class PassFailActivity extends GradedActivity
7 {
8
private double minPassingScore; // Minimum passing score
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10 /**
11
The constructor sets the minimum passing score.
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@param mps The minimum passing score.
13 */
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public PassFailActivity( double mps )
{
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minPassingScore = mps;
}
/**
The getGrade method returns a letter grade
determined from the score field. This
(Continued)
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method overrides the superclass method.
@return The letter grade.
*/
public char getGrade()
{
char letterGrade;
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37 }
38 }
// OVERRIDES supercalss method
if (super.getScore() >= minPassingScore)
letterGrade = 'P';
else
letterGrade = 'F';
return letterGrade;
Code Listing 10-22 (PassFailExam.java)
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/**
This class determines a passing or failing grade for
an exam.
*/
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public class PassFailExam extends PassFailActivity
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{
numQuestions;
private double pointsEach;
private int
numMissed;
private int
// Number of questions
// Points for each question
// Number of questions missed
/**
The constructor sets the number of questions, the
number of questions missed, and the minimum passing
score.
@param questions The number of questions.
@param missed The number of questions missed.
@param minPassing The minimum passing score.
*/
public PassFailExam( int questions, int missed,
double minPassing )
(Continued)
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{
super( minPassing );
/
double numericScore;
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// Set the numQuestions and numMissed fields.
numQuestions = questions;
numMissed = missed;
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// Calculate the points for each question and
// the numeric score for this exam.
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pointsEach = 100.0 / questions;
numericScore = 100.0 - (missed * pointsEach);
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// Call the superclass's setScore method to
// set the numeric score.
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// Does what? Required?
setScore( numericScore );
}
/**
(Continued)
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The getPointsEach method returns the number of
points each question is worth.
@return The value in the pointsEach field.
*/
public double getPointsEach()
{
return pointsEach;
}
/**
The getNumMissed method returns the number of
questions missed.
@return The value in the numMissed field.
*/
61 public int getNumMissed()
62 {
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return numMissed;
64 }
65 }
Code Listing 10-23 (PassFailExamDemo.java)
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import java.util.Scanner;
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public class PassFailExamDemo
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/**
This program demonstrates the PassFailExam class.
*/
{
public static void main(String[] args)
{
int
questions;
missed;
double minPassing
int
// Number of questions
// Number of questions missed
// Minimum passing score
// Create a Scanner object for keyboard input.
Scanner keyboard = new Scanner(System.in);
// Get the number of questions on the exam.
System.out.print("How many questions are " +
"on the exam? ");
questions = keyboard.nextInt();
(Continued)
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System.out.print("How many questions did " +
"the student miss? ");
missed = keyboard.nextInt();
System.out.print("What is the minimum " +
"passing score? ");
minPassing = keyboard.nextDouble();
// Create a PassFailExam object.
PassFailExam exam = new PassFailExam( questions, missed, minPassing );
System.out.println("Each question counts " +
exam.getPointsEach() + " points.");
System.out.println("The exam score is " +
exam.getScore());
(Continued)
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System.out.println("The exam grade is " +
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exam.getGrade());
48 }
49 }
Program Output with Example Input Shown in Bold
How many questions are on the exam? 100 [Enter]
How many questions did the student miss? 25 [Enter]
What is the minimum passing score? 60 [Enter]
Each question counts 1.0 points.
The exam score is 75.0
The exam grade is P
Code Listing 10-24 (ObjectMethods.java)
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/**
This program demonstrates the toString and equals
methods that are inherited from the Object class.
*/
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public class ObjectMethods
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{
public static void
{
main(String[] args)
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PassFailExam exam1 =
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PassFailExam exam2 =
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new PassFailExam(0, 0, 0);
new PassFailExam(0, 0, 0);
System.out.println( exam1 );
System.out.println( exam2 );
if (exam1.equals( exam2 ))
//
TESTS What?
(Continued)
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26 }
27 }
System.out.println("They are the same.");
else
System.out.println("They are not the same.");
Program Output
PassFailExam@16f0472
PassFailExam@18d107f
They are not the same.
Code Listing 10-25 (Polymorphic.java)
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/**
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This program demonstrates
*/
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public class Polymorphic
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polymorphic behavior.
{
public static void main(String[] args)
{
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GradedActivity[] tests = new GradedActivity[3];
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tests[0].setScore(95);
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tests[1] = new PassFailExam(20, 5, 60); // Why no method call to
// initialize “score”?
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tests[0] = new GradedActivity();
// The third test is the final exam. There were
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tests[2] = new FinalExam(50, 7);
26 // Display the grades.
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for (int i = 0; i < tests.length; i++)
{
System.out.println("Test " + (i + 1) + ": " +
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"score " + tests[i].getScore() +
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}
33 }
34 }
Program Output
", grade " + tests[i].getGrade());
Test 1: score 95.0, grade A
Test 2: score 75.0, grade P
Test 3: score 86.0, grade B
//
Why “p” grade?
Code Listing 10-26 (Student.java)
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/**
The Student class is an abstract class that holds
general data about a student. Classes representing
specific types of students should inherit from
this class.
*/
public abstract class Student
{
private String name;
private String idNumber;
private int yearAdmitted;
// Student name
// Student ID
// Year admitted
/**
The constructor sets the student's name,
ID number, and year admitted.
@param n The student's name.
@param id The student's ID number.
@param year The year the student was admitted.
*/
public Student(String n, String id, int year)
(Continued)
(Continued) Code Listing 10-26 (Student.java)
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{
name = n;
idNumber = id;
yearAdmitted = year;
}
/**
The toString method returns a String containing
the student's data.
@return A reference to a String.
*/
public String toString()
{
String str;
str = "Name: " + name
+ "\nID Number: " + idNumber
+ "\nYear Admitted: " + yearAdmitted;
return str;
}
(Continued)
(Continued) Code Listing 10-26 (Student.java)
45 /**
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The getRemainingHours method is abstract.
47
It must be overridden in a subclass.
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@return The hours remaining for the student.
49 */
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51 public abstract int getRemainingHours();
52 }
Code Listing 10-27 (CompSciStudent.java)
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/**
This class holds data for a computer science student.
*/
public class CompSciStudent extends Student
{
// Required hours
private final int MATH_HOURS = 20;
// Math hours
private final int CS_HOURS = 40;
// Comp sci hours
private final int GEN_ED_HOURS = 60; // Gen ed hours
// Hours taken
private int mathHours; // Math hours taken
private int csHours;
// Comp sci hours taken
private int genEdHours; // General ed hours taken
/**
The constructor sets the student's name,
ID number, and the year admitted.
@param n The student's name.
@param id The student's ID number.
@param year The year the student was admitted.
(Continued)
(Continued) Code Listing 10-27 (CompSciStudent.java)
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*/
public CompSciStudent(String n, String id, int year)
{
super(n, id, year);
}
/**
The setMathHours method sets the number of
math hours taken.
@param math The math hours taken.
*/
public void setMathHours(int math)
{
mathHours = math;
}
/**
The setCsHours method sets the number of
computer science hours taken.
(Continued)
(Continued) Code Listing 10-27 (CompSciStudent.java)
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@param cs The computer science hours taken.
*/
public void setCsHours(int cs)
{
csHours = cs;
}
/**
The setGenEdHours method sets the number of
general ed hours taken.
@param genEd The general ed hours taken.
*/
public void setGenEdHours(int genEd)
{
genEdHours = genEd;
}
/**
The getRemainingHours method returns the
number of hours remaining to be taken.
(Continued)
(Continued) Code Listing 10-27 (CompSciStudent.java)
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@return The hours remaining for the student.
*/
public int getRemainingHours()
{
int reqHours,
// Total required hours
remainingHours;
// Remaining hours
// Calculate the required hours.
reqHours = MATH_HOURS + CS_HOURS + GEN_ED_HOURS;
// Calculate the remaining hours.
remainingHours = reqHours - (mathHours + csHours
+ genEdHours);
return remainingHours;
}
/**
The toString method returns a string containing
the student's data.
@return A reference to a String.
(Continued)
(Continued) Code Listing 10-27 (CompSciStudent.java)
89 */
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91 public String toString()
92 {
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String str;
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str = super.toString() +
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"\nMajor: Computer Science" +
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"\nMath Hours Taken: " + mathHours +
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"\nComputer Science Hours Taken: " + csHours +
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"\nGeneral Ed Hours Taken: " + genEdHours;
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return str;
102 }
103 }
Code Listing 10-28 (CompSciStudentDemo.java)
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/**
This program demonstrates the CompSciStudent class.
*/
public class CompSciStudentDemo
{
public static void main(String[] args)
{
// Create a CompSciStudent object.
CompSciStudent csStudent =
new CompSciStudent("Jennifer Haynes",
"167W98337", 2004);
// Store values for math, CS, and gen ed hours.
csStudent.setMathHours(12);
csStudent.setCsHours(20);
csStudent.setGenEdHours(40);
// Display the student's data.
System.out.println(csStudent);
// Display the number of remaining hours.
(Continued) Code Listing 10-28 (CompSciStudentDemo.java)
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System.out.println("Hours remaining: " +
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csStudent.getRemainingHours());
25 }
26 }
Program Output
Name: Jennifer Haynes
ID Number: 167W98337
Year Admitted: 2004
Major: Computer Science
Math Hours Taken: 12
Computer Science Hours Taken: 20
General Ed Hours Taken: 40
Hours remaining: 48
Code Listing 10-29 (Relatable.java)
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/**
Relatable interface
*/
public interface Relatable
{
boolean equals(GradedActivity g);
boolean isGreater(GradedActivity g);
boolean isLess(GradedActivity g);
}
Code Listing 10-30 (FinalExam3.java)
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/**
This class determines the grade for a final exam.
*/
public class FinalExam3 extends GradedActivity
implements Relatable
{
private int numQuestions;
// Number of questions
private double pointsEach;
// Points for each question
private int numMissed;
// Questions missed
/**
The constructor sets the number of questions on the
exam and the number of questions missed.
@param questions The number of questions.
@param missed The number of questions missed.
*/
public FinalExam3(int questions, int missed)
{
double numericScore;
// To hold a numeric score
(Continued)
(Continued) Code Listing 10-30 (FinalExam3.java)
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// Set the numQuestions and numMissed fields.
numQuestions = questions;
numMissed = missed;
// Calculate the points for each question and
// the numeric score for this exam.
pointsEach = 100.0 / questions;
numericScore = 100.0 - (missed * pointsEach);
// Call the inherited setScore method to
// set the numeric score.
setScore(numericScore);
}
/**
The getPointsEach method returns the number of
points each question is worth.
@return The value in the pointsEach field.
*/
public double getPointsEach()
{
(Continued)
(Continued) Code Listing 10-30 (FinalExam3.java)
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return pointsEach;
}
/**
The getNumMissed method returns the number of
questions missed.
@return The value in the numMissed field.
*/
public int getNumMissed()
{
return numMissed;
}
/**
The equals method compares the calling object
to the argument object for equality.
@return true if the calling
object's score is equal to the argument's
score.
*/
(Continued)
(Continued) Code Listing 10-30 (FinalExam3.java)
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public boolean equals(GradedActivity g)
{
boolean status;
if (this.getScore() == g.getScore())
status = true;
else
status = false;
return status;
}
/**
The isGreater method determines whether the calling
object is greater than the argument object.
@return true if the calling object's score is
greater than the argument object's score.
*/
public boolean isGreater(GradedActivity g)
{
boolean status;
(Continued)
(Continued) Code Listing 10-30 (FinalExam3.java)
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if (this.getScore() > g.getScore())
status = true;
else
status = false;
return status;
}
/**
The isLess method determines whether the calling
object is less than the argument object.
@return true if the calling object's score is
less than the argument object's score.
*/
public boolean isLess(GradedActivity g)
{
boolean status;
if (this.getScore() < g.getScore())
status = true;
(Continued)
(Continued) Code Listing 10-30 (FinalExam3.java)
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115 }
116 }
else
status = false;
return status;
Code Listing 10-31 (InterfaceDemo.java)
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/**
This program demonstrates the FinalExam3 class, which
implements the Relatable interface.
*/
public class InterfaceDemo
{
public static void main(String[] args)
{
// Exam #1 had 100 questions and the student
// missed 20 questions.
FinalExam3 exam1 = new FinalExam3(100, 20);
// Exam #2 had 100 questions and the student
// missed 30 questions.
FinalExam3 exam2 = new FinalExam3(100, 30);
// Display the exam scores.
System.out.println("Exam 1: " +
exam1.getScore());
System.out.println("Exam 2: " +
exam2.getScore());
(Continued)
(Continued) Code Listing 10-31 (InterfaceDemo.java)
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// Compare the exam scores.
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if (exam1.equals(exam2))
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System.out.println("The exam scores " +
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"are equal.");
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if (exam1.isGreater(exam2))
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System.out.println("The Exam 1 score " +
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"is the highest.");
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if (exam1.isLess(exam2))
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System.out.println("The Exam 1 score " +
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"is the lowest.");
36 }
37 }
Program Output
Exam 1: 80.0
Exam 2: 70.0
The Exam 1 score is the highest.
Code Listing 10-32 (RetailItem.java)
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/**
RetailItem interface
*/
public interface RetailItem
{
public double getRetailPrice();
}
Code Listing 10-33 (CompactDisc.java)
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/**
Compact Disc class
*/
public class CompactDisc implements RetailItem
{
private String title;
// The CD's title
private String artist;
// The CD's artist
private double retailPrice;
// The CD's retail price
/**
Constructor
@param cdTitle The CD title.
@param cdArtist The name of the artist.
@param cdPrice The CD's price.
*/
public CompactDisc(String cdTitle, String cdArtist,
double cdPrice)
{
title = cdTitle;
artist = cdArtist;
(Continued)
(Continued) Code Listing 10-33 (CompactDisc.java)
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retailPrice = cdPrice;
}
/**
getTitle method
@return The CD's title.
*/
public String getTitle()
{
return title;
}
/**
getArtist method
@return The name of the artist.
*/
public String getArtist()
{
return artist;
}
(Continued)
(Continued) Code Listing 10-33 (CompactDisc.java)
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46 /**
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getRetailPrice method (Required by the RetailItem
48
interface)
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@return The retail price of the CD.
50 */
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52 public double getRetailPrice()
53 {
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return retailPrice;
55 }
56 }
Code Listing 10-34 (DvdMovie.java)
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/**
DvdMovie class
*/
public class DvdMovie implements RetailItem
{
private String title;
// The DVD's title
private int runningTime;
// Running time in minutes
private double retailPrice;
// The DVD's retail price
/**
Constructor
@param dvdTitle The DVD title.
@param runTime The running time in minutes.
@param dvdPrice The DVD's price.
*/
public DvdMovie(String dvdTitle, int runTime,
double dvdPrice)
{
title = dvdTitle;
runningTime = runTime;
(Continued)
(Continued) Code Listing 10-34 (DvdMovie.java)
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retailPrice = dvdPrice;
}
/**
getTitle method
@return The DVD's title.
*/
public String getTitle()
{
return title;
}
/**
getRunningTime method
@return The running time in minutes.
*/
public int getRunningTime()
{
return runningTime;
}
(Continued)
(Continued) Code Listing 10-34 (DvdMovie.java)
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46 /**
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getRetailPrice method (Required by the RetailItem
48
interface)
49
@return The retail price of the DVD.
50 */
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52 public double getRetailPrice()
53 {
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return retailPrice;
55 }
56 }
Code Listing 10-35 (PolymorphicInterfaceDemo.java)
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/**
This program demonstrates that an interface type may
be used to create a polymorphic reference.
*/
public class PolymorphicInterfaceDemo
{
public static void main(String[] args)
{
// Create a CompactDisc object.
CompactDisc cd =
new CompactDisc("Greatest Hits",
"Joe Looney Band",
18.95);
// Create a DvdMovie object.
DvdMovie movie =
new DvdMovie("Wheels of Fury",
137, 12.95);
// Display the CD's title.
System.out.println("Item #1: " +
cd.getTitle());
(Continued)
(Continued) Code Listing 10-35 (PolymorphicInterfaceDemo.java)
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// Display the CD's price.
showPrice(cd);
// Display the DVD's title.
System.out.println("Item #2: " +
movie.getTitle());
// Display the DVD's price.
showPrice(movie);
}
/**
The showPrice method displays the price
of a RetailItem object.
@param item A reference to a RetailItem object.
*/
private static void showPrice(RetailItem item)
{
System.out.printf("Price: $%,.2f\n", item.getRetailPrice());
}
(Continued)
(Continued) Code Listing 10-35 (PolymorphicInterfaceDemo.java)
45 }
Program Output
Item #1: Greatest Hits
Price: $18.95
Item #2: Wheels of Fury
Price: $12.95