в 16:40, 26 мая 2010

2010-05-26T16:40:06Z

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2010-05-26T12:42:45Z

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==Demonstrate polymorphism in Point-Circle-Cylinder hierarchy==

<source lang="vbnet">
Imports System
Public Class MainClass
Shared Sub Main(ByVal args As String())
" instantiate Point, Circle and Cylinder objects
Dim point As New Point(7, 11)
Dim circle As New Circle(22, 8, 3.5)
Dim cylinder As New Cylinder(10, 10, 3.3, 10)
" instantiate array of base-class references
Dim arrayOfShapes As CShape() = New CShape(2) {}
" arrayOfShapes(0) refers to Point object
arrayOfShapes(0) = point
" arrayOfShapes(1) refers to Circle object
arrayOfShapes(1) = circle
" arrayOfShapes(2) refers to Cylinder object
arrayOfShapes(2) = cylinder
Console.WriteLine( point.Name & ": " & _
point.ToString() & vbCrLf & circle.Name & ": " & _
circle.ToString() & vbCrLf & cylinder.Name & _
": " & cylinder.ToString() )
Dim shape As CShape
For Each shape In arrayOfShapes
Console.WriteLine( vbCrLf & vbCrLf & shape.Name & ": " & _
shape.ToString() & vbCrLf & "Area = " & _
String.Format("{0:F}", shape.Area) & vbCrLf & _
"Volume = " & String.Format("{0:F}", shape.Volume) )
Next
End Sub
End Class
Public MustInherit Class CShape
" return shape area
Public Overridable Function Area() As Double
Return 0
End Function " Area
" return shape volume
Public Overridable Function Volume() As Double
Return 0
End Function " Volume
" overridable method that should return shape name
Public MustOverride ReadOnly Property Name() As String
End Class " CShape

Public Class Circle
Inherits Point " Circle Inherits from class Point
Private mRadius As Double
" default constructor
Public Sub New()
" implicit call to Point constructor occurs here
Radius = 0
End Sub " New
" constructor
Public Sub New(ByVal xValue As Integer, _
ByVal yValue As Integer, ByVal radiusValue As Double)
" use MyBase reference to Point constructor explicitly
MyBase.New(xValue, yValue)
Radius = radiusValue
End Sub " New
" property Radius
Public Property Radius() As Double
Get
Return mRadius
End Get
Set(ByVal radiusValue As Double)
If radiusValue >= 0 Then " mRadius must be nonnegative
mRadius = radiusValue
End If
End Set
End Property " Radius
" calculate Circle diameter
Public Function Diameter() As Double
Return mRadius * 2
End Function " Diameter
" calculate Circle circumference
Public Function Circumference() As Double
Return Math.PI * Diameter()
End Function " Circumference
" calculate Circle area
Public Overrides Function Area() As Double
Return Math.PI * mRadius ^ 2
End Function " Area
" return String representation of Circle
Public Overrides Function ToString() As String
" use MyBase to return Circle String representation
Return "Center= " & MyBase.ToString() & _
"; Radius = " & mRadius
End Function " ToString
" override property Name from class Point
Public Overrides ReadOnly Property Name() As String
Get
Return "Circle"
End Get
End Property " Name
End Class
Public Class Cylinder
Inherits Circle " Cylinder inherits from class Circle
Private mHeight As Double
" default constructor
Public Sub New()
" implicit call to Circle constructor occurs here
Height = 0
End Sub " New
" four-argument constructor
Public Sub New(ByVal xValue As Integer, _
ByVal yValue As Integer, ByVal radiusValue As Double, _
ByVal heightValue As Double)
" explicit call to Circle constructor
MyBase.New(xValue, yValue, radiusValue)
Height = heightValue " set Cylinder height
End Sub " New
" property Height
Public Property Height() As Double
Get
Return mHeight
End Get
" set Cylinder height if argument value is positive
Set(ByVal heightValue As Double)
If heightValue >= 0 Then " mHeight must be nonnegative
mHeight = heightValue
End If
End Set
End Property " Height
" override method Area to calculate Cylinder surface area
Public Overrides Function Area() As Double
Return 2 * MyBase.Area + MyBase.Circumference * mHeight
End Function " Area
" calculate Cylinder volume
Public Overrides Function Volume() As Double
Return MyBase.Area * mHeight
End Function " Volume
" convert Cylinder to String
Public Overrides Function ToString() As String
Return MyBase.ToString() & "; Height = " & mHeight
End Function " ToString
" override property Name from class Circle
Public Overrides ReadOnly Property Name() As String
Get
Return "Cylinder"
End Get
End Property " Name
End Class
Public Class Point
Inherits CShape " Point inherits from MustInherit class CShape
" point coordinate
Private mX, mY As Integer
" default constructor
Public Sub New()
" implicit call to Object constructor occurs here
X = 0
Y = 0
End Sub " New
" constructor
Public Sub New(ByVal xValue As Integer, _
ByVal yValue As Integer)
" implicit call to Object constructor occurs here
X = xValue
Y = yValue
End Sub " New
" property X
Public Property X() As Integer
Get
Return mX
End Get
Set(ByVal xValue As Integer)
mX = xValue " no need for validation
End Set
End Property " X
" property Y
Public Property Y() As Integer
Get
Return mY
End Get
Set(ByVal yValue As Integer)
mY = yValue " no need for validation
End Set
End Property " Y
" return String representation of Point
Public Overrides Function ToString() As String
Return "[" & mX & ", " & mY & "]"
End Function " ToString
" implement MustOverride property of class CShape
Public Overrides ReadOnly Property Name() As String
Get
Return "Point"
End Get
End Property " Name
End Class

</source>

==PolyMorphism At Work==

<source lang="vbnet">
Imports System
Imports System.Collections

Public Class MainClass
Shared Sub Main()
Dim e1 As New Employee("Employee", 5)
Dim e2 As New Programmer("Programmer", 15)
Dim e3 As New Archictect("Archictect", 15)
Dim ourEmployees(2) As Employee

ourEmployees(0) = e1
ourEmployees(1) = e2
ourEmployees(2) = e3

Dim anEmployee As Employee
For Each anEmployee In ourEmployees
anEmployee.RaiseSalary(0.1D)
Console.WriteLine(anEmployee.TheName & " salary now is " & anEmployee.Salary())
Next
End Sub

End Class
Public Class Employee
Private m_Name As String
Private m_Salary As Decimal
Public Sub New(ByVal theName As String, ByVal curSalary As Decimal)
m_Name = TheName
m_Salary = curSalary
End Sub
Public ReadOnly Property TheName() As String
Get
Return m_Name
End Get
End Property
Public ReadOnly Property Salary() As Decimal
Get
Return MyClass.m_Salary
End Get
End Property
Public Overridable Overloads Sub RaiseSalary(ByVal Percent As Decimal)
m_Salary = (1 + Percent) * m_Salary
End Sub
End Class
Public Class Programmer
Inherits Employee
Public Sub New(ByVal theName As String, ByVal curSalary As Decimal)
MyBase.New(theName, curSalary)
End Sub
Public Overloads Overrides Sub RaiseSalary(ByVal Percent As Decimal)
MyBase.RaiseSalary(1.2D * Percent)
End Sub
End Class
Public Class Archictect
Inherits Programmer
Public Sub New(ByVal theName As String, ByVal curSalary As Decimal)
MyBase.New(theName, curSalary)
End Sub
Public Overloads Overrides Sub RaiseSalary(ByVal Percent As Decimal)
MyBase.RaiseSalary(2D * Percent)
End Sub
End Class

</source>

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