chapter 9 – object-oriented programming: inheritance

2002 Prentice Hall. All rights reserved.

1

Chapter 9 – Object-Oriented Programming: Inheritance

Outline9.1 Introduction9.2 Base Classes and Derived Classes9.3 protected Members9.4 Creating Base Classes and Derived Classes9.5 Constructors and Destructors in Derived Classes9.6 Software Engineering with Inheritance9.7 Case Study: Point, Circle, Cylinder


2

9.2 Base Classes and Derived Classes

Base class Derived classes Student GraduateStudent

UndergraduateStudent

Shape Circle Triangle Rectangle

Loan CarLoan HomeImprovementLoan MortgageLoan

Employee FacultyMember StaffMember

Account CheckingAccount SavingsAccount

Fig. 9.1 Inheritance examples.


3


Fig. 9.2 Inheritance hierarchy for university CommunityMembers.

CommunityMemeber

Employee Student Alumnus

Faculty Staff

Administrator Teacher


4


Fig. 9.3 Portion of a Shape class hierarchy.

Shape

TwoDimensionalShape ThreeDimensionalShape

Sphere Cube CylinderTriangleSquareCircle

2002 Prentice Hall.All rights reserved.

Outline5

Point.cs

1 // Fig. 9.4: Point.cs2 // Class Point maintains an X and Y coordinate.3 4 using System;5 6 // Point class definition7 public class Point 8 {9 // point coordinate10 protected int xCoordinate, yCoordinate;11 12 // default constructor13 public Point()14 {15 // implicit call to base class constructor occurs here16 X = 0;17 Y = 0;18 }19 20 // constructor21 public Point( int xValue, int yValue )22 {23 // implicit call to base class constructor occurs here24 X = xValue;25 Y = yValue;26 }27 28 // property X29 public int X30 {31 get32 {33 return xCoordinate;34 }35


Outline6

Point.cs

Program Output

36 set 37 {38 xCoordinate = value;39 }40 }41 42 // property Y43 public int Y44 {45 get46 {47 return yCoordinate;48 }49 50 set 51 {52 yCoordinate = value;53 }54 }55 56 // return string representation of Point57 public override string ToString()58 {59 return "[" + X + ", " + Y + "]";60 }61 62 } // end class Point


Outline7

PointTest.cs

1 // Fig. 9.5: PointTest.cs2 // Manipulating a Point object.3 4 using System;5 using System.Windows.Forms;6 7 // PointTest class definition8 class PointTest9 {10 // main entry point for application11 static void Main( string[] args )12 {13 Point point = new Point( 72, 115 );14 15 // append initial Point coordinates to output16 string output = "X coordinate: " + point.X +17 "\nY coordinate: " + point.Y;18 19 // set new coordinates20 point.X = 10;21 point.Y = 10;22 23 // append new Point coordinates to output24 output += "\n\nNew location of point: " + 25 point.ToString() + "\nImplicit ToString call: " +26 point;27 28 MessageBox.Show( output, "Demonstrating Class Point" );29 30 } // end method Main31 32 } // end class PointTest


Outline8

Circle.cs

1 // Fig. 9.6: Circle.cs2 // Class Circle maintains a radius and X and Y coordinates 3 // representing a circle's center.4 5 using System;6 7 // Circle class definition8 public class Circle 9 {10 // coordinates of circle center11 protected int xCoordinate, yCoordinate;12 13 // radius of circle14 protected double radius;15 16 // default constructor17 public Circle()18 {19 // implicit call to base class constructor occurs here20 X = 0;21 Y = 0;22 Radius = 0.0;23 }24 25 // constructor26 public Circle( int xValue, int yValue, double radiusValue )27 {28 // implicit call to base class constructor occurs here29 X = xValue;30 Y = yValue;31 Radius = radiusValue;32 }33


Outline9

Circle.cs

34 // property X35 public int X36 {37 get38 {39 return xCoordinate;40 }41 42 set 43 {44 xCoordinate = value;45 }46 }47 48 // property Y49 public int Y50 {51 get52 {53 return yCoordinate;54 }55 56 set 57 {58 yCoordinate = value;59 }60 }61 62 // property Radius63 public double Radius64 {65 get66 {67 return radius;68 }


Outline10

Circle.cs

69 70 set 71 {72 radius = ( value >= 0.0 ? value : 0.0 );73 }74 }75 76 // return area of Circle77 public double Area()78 {79 return Math.PI * radius * radius;80 }81 82 // return string representation of Circle83 public override string ToString()84 {85 return "Center = [" + X + ", " + Y + 86 "]; Radius = " + radius;87 }88 89 } // end class Circle


Outline11

CircleTest.cs

1 // Fig. 9.7: CircleTest.cs2 // Manipulating a Circle object.3 4 using System;5 using System.Windows.Forms;6 7 // CircleTest class definition8 class CircleTest9 {10 // main entry point for application11 static void Main( string[] args )12 {13 Circle circle = new Circle( 37, 43, 2.5 );14 15 // append Circle properties to output16 string output = "X coordinate: " + circle.X +17 "\nY coordinate: " + circle.Y + 18 "\nRadius: " + circle.Radius;19 20 // set new coordinates and radius21 circle.X = 10;22 circle.Y = 10;23 circle.Radius = 4.25;24 25 // append new Point coordinates to output26 output += "\n\nNew location and radius of circle: " + 27 circle.ToString() + 28 "\nImplicit ToString call: " + circle + "\nArea: " +29 String.Format( "{0:F2}", circle.Area() );30 31 MessageBox.Show( output, "Demonstrating Class Circle" );32 33 } // end method Main34 35 } // end class CircleTest


Outline12

CircleTest.cs Program Output


Outline13

Circle.cs

1 // Fig. 9.8: Circle.cs2 // Class Circle inherits from Point.3 4 using System;5 6 // Circle class definition7 public class Circle : Point8 {9 // radius of circle10 protected double radius;11 12 // default constructor13 public Circle()14 {15 // implicit call to base class constructor occurs here16 Radius = 0.0;17 }18 19 // constructor20 public Circle( int xValue, int yValue, double radiusValue )21 : base( xValue, yValue )22 {23 Radius = radiusValue;24 }25 26 // property Radius27 public double Radius28 {29 get30 {31 return radius;32 }33


Outline14

Circle.cs

34 set 35 {36 radius = ( value >= 0.0 ? value : 0.0 );37 }38 }39 40 // return area of Circle41 public double Area()42 {43 return Math.PI * radius * radius;44 }45 46 // return string representation of Circle47 public override string ToString()48 {49 return "Center = [" + xCoordinate + ", " + yCoordinate +50 "]; Radius = " + radius;51 }52 53 } // end class Circle


Outline15

Point.cs

1 // Fig. 9.9: Point.cs2 // Class Point maintains an X and Y coordinate.3 4 using System;5 6 // Point class definition7 public class Point 8 {9 // point coordinate10 protected int xCoordinate, yCoordinate;11 12 // default constructor13 public Point()14 {15 // implicit call to base class constructor occurs here16 X = 0;17 Y = 0;18 Console.WriteLine( "Point constructor: " + this );19 }20 21 // constructor22 public Point( int xValue, int yValue )23 {24 // implicit call to base class constructor occurs here25 X = xValue;26 Y = yValue;27 Console.WriteLine( "Point constructor: " + this );28 }29 30 // destructor31 ~Point()32 { 33 Console.WriteLine( "Point destructor: " + this );34 }35


Outline16

Point.cs

36 // property X37 public int X38 {39 get40 {41 return xCoordinate;42 }43 44 set 45 {46 xCoordinate = value;47 }48 }49 50 // property Y51 public int Y52 {53 get54 {55 return yCoordinate;56 }57 58 set 59 {60 yCoordinate = value;61 }62 }63 64 // return string representation of Point65 public override string ToString()66 {67 return "[" + X + ", " + Y + "]";68 }69 70 } // end class Point


Outline17

Circle.cs

1 // Fig. 9.10: Circle.cs2 // Class Circle inherits from Point.3 4 using System;5 6 // Circle class definition7 public class Circle : Point8 {9 // radius of circle10 protected double radius;11 12 // default constructor13 public Circle()14 {15 // implicit call to base class constructor occurs here16 Radius = 0.0;17 Console.WriteLine( "Circle constructor: " + this );18 }19 20 // constructor 21 public Circle( int xValue, int yValue, double radiusValue )22 : base( xValue, yValue )23 {24 Radius = radiusValue;25 Console.WriteLine( "Circle constructor: " + this );26 }27 28 // destructor29 ~Circle()30 {31 Console.WriteLine( "Circle destructor: " + this );32 }33


Outline18

Circle.cs

34 // property Radius35 public double Radius36 {37 get38 {39 return radius;40 }41 42 set 43 {44 radius = ( value >= 0.0 ? value : 0.0 );45 }46 }47 48 // return string representation of Circle49 public override string ToString()50 {51 return "Center = " + base.ToString() + 52 "; Radius = " + radius;53 }54 55 } // end class Circle


Outline19

ConstructorAndDestructor.cs

1 // Fig. 9.11: ConstructorAndDestructor.cs2 // Demonstrating the order in which base-class and 3 // derived-class constructors and destructors are called.4 5 using System;6 7 // ConstructorAndDestructor class definition8 class ConstructorAndDestructor9 {10 // main entry point for application11 static void Main( string[] args )12 {13 Circle circle1 = new Circle( 72, 29, 4.5 );14 15 Console.WriteLine();16 17 Circle circle2 = new Circle( 5, 5, 10 );18 19 Console.WriteLine();20 21 // remove references to Circle objects22 circle1 = null;23 circle2 = null;24 25 System.GC.Collect();26 27 } // end method Main28 29 } // end class ConstructorAndDestructor


Outline20

ConstructorAndDestructor.cs Program Output

Point constructor: Center = [72, 29]; Radius = 0Circle constructor: Center = [72, 29]; Radius = 4.5

Point constructor: Center = [5, 5]; Radius = 0Circle constructor: Center = [5, 5]; Radius = 10

Circle destructor: Center = [5, 5]; Radius = 10Point destructor: Center = [5, 5]; Radius = 10Circle destructor: Center = [72, 29]; Radius = 4.5Point destructor: Center = [72, 29]; Radius = 4.5


Outline21

Circle.cs

1 // Fig. 9.12: Circle.cs2 // Class Circle inherits from Point.3 4 using System;5 6 // Circle class definition7 public class Circle : Point8 {9 // radius of circle10 protected double radius;11 12 // default constructor13 public Circle()14 {15 // implicit call to base class constructor occurs here16 Radius = 0.0;17 }18 19 // constructor20 public Circle( int xValue, int yValue, double radiusValue )21 : base( xValue, yValue )22 {23 Radius = radiusValue;24 }25 26 // property Radius27 public double Radius28 {29 get30 {31 return radius;32 }33


Outline22

Circle.cs

34 set 35 {36 radius = ( value >= 0.0 ? value : 0.0 );37 }38 }39 40 // return area of Circle41 public virtual double Area()42 {43 return Math.PI * radius * radius;44 }45 46 // return string representation of Circle47 public override string ToString()48 {49 return "Center = " + base.ToString() + 50 "; Radius = " + radius;51 }52 53 } // end class Circle


Outline23

CircleTest2.cs

1 // Fig. 9.13: CircleTest2.cs2 // Manipulating a Circle object.3 4 using System;5 using System.Windows.Forms;6 7 // CircleTest class definition8 class CircleTest29 {10 // main entry point for application11 static void Main( string[] args )12 {13 Circle circle = new Circle( 37, 43, 2.5 );14 15 // append Circle properties to output16 string output = "X coordinate: " + circle.X +17 "\nY coordinate: " + circle.Y + 18 "\nRadius: " + circle.Radius;19 20 // set new coordinates and radius21 circle.X = 10;22 circle.Y = 10;23 circle.Radius = 4.25;24 25 // append new Point coordinates to output26 output += "\n\nNew location and radius of circle: " + 27 circle.ToString() + 28 "\nImplicit ToString call: " + circle + "\nArea: " +29 String.Format( "{0:F2}", circle.Area() );30 31 MessageBox.Show( output, "Demonstrating Class Circle" );32 33 } // end method Main34 35 } // end class CircleTest2


Outline24

CircleTest2.cs Program Output


Outline25

Cylinder.cs

1 // Fig. 9.14: Cylinder.cs2 // Class Cylinder inherits from Circle.3 4 using System;5 6 // Cylinder class definition7 public class Cylinder : Circle8 {9 protected double height;10 11 // default constructor12 public Cylinder()13 {14 // implicit call to base class constructor occurs here15 Height = 0.0;16 }17 18 // constructor19 public Cylinder( int xValue, int yValue, 20 double radiusValue, double heightValue )21 : base( xValue, yValue, radiusValue )22 {23 Height = heightValue;24 }25 26 // property Height27 public double Height28 {29 get30 {31 return height;32 }33


Outline26

Cylinder.cs

34 set35 {36 height = ( value >= 0.0 ? value : 0.0 );37 }38 }39 40 // return area of Cylinder41 public override double Area()42 {43 return 2 * base.Area() + 2 * Math.PI * radius * radius;44 }45 46 // return volume of Cylinder47 public double Volume()48 {49 return base.Area() * height;50 }51 52 // return string representation of Cylinder53 public override string ToString()54 {55 return base.ToString() + "; Heigth = " + height;56 }57 58 } // end class Cylinder


Outline27

CylinderTest.cs

1 // Fig. 9.15: CylinderTest.cs2 // Manipulating a Cylinder object.3 4 using System;5 using System.Windows.Forms;6 7 // CylinderTest class definition8 class CylinderTest9 {10 // main entry point for application11 static void Main( string[] args )12 {13 Cylinder cylinder = new Cylinder( 12, 23, 2.5, 5.7 );14 15 // append Cylinder properties to output16 string output = "X coordinate: " + cylinder.X +17 "\nY coordinate: " + cylinder.Y + 18 "\nRadius: " + cylinder.Radius + 19 "\nHeight: " + cylinder.Height;20 21 // set new coordinates and radius22 cylinder.X = 10;23 cylinder.Y = 10;24 cylinder.Radius = 10;25 cylinder.Height = 4.25;26 27 // append new Point coordinates to output28 output += 29 "\n\nNew location, radius and height of cylinder: " + 30 cylinder.ToString() + "\nImplicit ToString call: " +31 cylinder + "\nArea: " +32 String.Format( "{0:F2}", cylinder.Area() ) + 33 "\nVolume: " + 34 String.Format( "{0:F2}", cylinder.Volume() );35


Outline28

CylinderTest.cs

Program Output

36 MessageBox.Show( output, "Demonstrating Class Cylinder" );37 38 } // end method Main39 40 } // end class CylinderTest

chapter 9 – object-oriented programming: inheritance

Documents