Comparing Object-Oriented Languages, Page 5

Public MustInherit Class Shape

   Protected area As Double

   Public MustOverride Function getArea() As Double

End Class

Public Class Rectangle

   Inherits Shape

   Dim length As Double
   Dim width As Double

   Sub New(ByVal l As Double, ByVal w As Double)

      length = l
      width = w

   End Sub

   Public Overrides Function getArea() As Double

      area = length * width
      Return area

   End Function

End Class

Public Class Circle

   Inherits Shape

   Dim radius As Double

   Sub New(ByVal r As Double)

      radius = r

   End Sub

   Public Overrides Function getArea() As Double

      area = 3.14 * (radius * radius)
      Return area

   End Function

End Class

Module Module1

   Sub Main()

      Dim myCircle As New Circle(2.2)
      Dim myRectangle As New Rectangle(2.2, 3.3)
      Dim result As Double

      result = myCircle.getArea()
      System.Console.Write("Circle area =  ")
      System.Console.WriteLine(result)

      result = myRectangle.getArea()
      System.Console.Write("Rectangle area =  ")
      System.Console.WriteLine(result)

      System.Console.Read()
   End Sub

End Module

Listing 3c: VB Code for Shape

Conclusion

In this article, you changed gears a bit. Rather than focus on a specific programming concept or technique, you inspected several basic applications and concentrated on how to develop the application in three different object-oriented languages: Java, C#, and VB .NET.

The intent was to whet your appetite. In future articles, you will delve deeper and compare specific programming features and see how the various languages implement these features. You also will compare the similarities and the differences of the various languages. Exploring different languages can help you better understand object-oriented concepts.

References

Weisfeld, M.A. (2005). "The Evolution of Object-Oriented Languages," Developer.com.

About the Author

Matt Weisfeld is a faculty member at Cuyahoga Community College (Tri-C) in Cleveland, Ohio. Matt is a member of the Information Technology department, teaching programming languages such as C++, Java, C#, and .NET, as well as various web technologies. Prior to joining Tri-C, Matt spent 20 years in the information technology industry, gaining experience in software development, project management, business development, corporate training, and part-time teaching. Matt holds an MS in computer science and an MBA in project management. Besides The Object-Oriented Thought Process, which is now in its second edition, Matt has published two other computer books, and more than a dozen articles in magazines and journals such as Dr. Dobb's Journal, The C/C++ Users Journal, Software Development Magazine, Java Report, and the international journal Project Management. Matt has presented at conferences throughout the United States and Canada.