This week's book giveaway is in the Other Languages forum.
We're giving away four copies of Functional Reactive Programming and have Stephen Blackheath and Anthony Jones on-line!
See this thread for details.
Win a copy of Functional Reactive Programming this week in the Other Languages forum!
  • Post Reply
  • Bookmark Topic Watch Topic
  • New Topic

abstract class constructors

 
preeti khane
Ranch Hand
Posts: 93
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Can an abstract class have constructors?

I would have thought no , as they cannot be instantiated , so there is no real purpose... Am I right?
 
Marlene Miller
Ranch Hand
Posts: 1392
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Yes, an abstract class can have constructors.
An abstract class may have instance variables and non-abstract methods (common to all concrete subclasses) that operate on those variables. A constructor could be used to initialize the instance variables.
A constructor of a concrete subclass would invoke the superclass constructor to initialize the variables of the abstract superclass.
 
Marlene Miller
Ranch Hand
Posts: 1392
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Graph is part of a framework. It supplies nearly all of the methods to support a generic graph editor.
SimpleGraph is a client-defined extension that supplies the geometric shapes of the nodes and edges to be used in the graph.

Graph is an abstract class. It needs a constructor to initialize the variables to do its work.

(From Cay Horstmann´┐Żs Object Oriented Design & Patterns)
[ May 27, 2003: Message edited by: Marlene Miller ]
 
  • Post Reply
  • Bookmark Topic Watch Topic
  • New Topic