RE: Java Question on Inheritance
Ultimately, I want to get the thumb of this Image and convert it to a URL. I want to be able to do this efficiently and use something like the following syntax. myImage.getThumb().toURL() Is this possible? Yes, but getThumb() must return a subclass of SuperOne. --- Michael Wentzel Software Developer Software As We Think - http://www.aswethink.com mailto:[EMAIL PROTECTED] - Punisher of those who cannot spell dumb!
RE: Java Question on Inheritance
No.
The way you are doing means you are calling .toURL() method on what ever is
returned by the method getThumb(). Unless getThumb returns a type of Object of
type SuperOne or it's sub-class you cannot call this method and you should see a
compile time error.
What
you can do is
URL
url = toURL( myImage.getThumb() ); in your SuperOne or its
sub-class.
=== Gary
Grewal
-Original Message-From: Ryan
[mailto:[EMAIL PROTECTED]]Sent: Thursday, March 22, 2001 10:38
AMTo: [EMAIL PROTECTED]Subject: Java
Question on Inheritance
I don't really know what to call what I'm having trouble with but here is
what I am trying to do.
I have asuperclass called SuperOne, it has a method to convert a
string to a URL formatcalled toURL().
I havean Image class that is a subclass of SuperOne. It holds
astringstoringthe local path of the image
onmyharddrive. This subclass contains a method to get the
corresponding thumbnail of the image on my harddrive. The method is called
getThumb().
Ina thirdclass I want to instantiate an Image object
something like:
Image myImage = new Image("/home/pic.gif");
Ultimately, I want to get the thumb of this Image and convert it to a
URL. I want to be able to do this efficiently and use something like the
following syntax.
myImage.getThumb().toURL()
Is this possible?
thanx
-ryan
Re: Java Question on Inheritance
Then this is my next problem.
I currently have getThumb() returning an Image object.
The part where I am stuck at is what to do in the toURL() method.
my mock getThumb() method currently looks something like
public Image getThumb(){
this.iValue = "/home/thumbs";
return this;
}
-ryan
- Original Message -
From: "Michael Wentzel" [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Thursday, March 22, 2001 8:32 AM
Subject: RE: Java Question on Inheritance
Ultimately, I want to get the thumb of this Image and convert it to a
URL.
I want to be able to do this efficiently and use something like the
following syntax.
myImage.getThumb().toURL()
Is this possible?
Yes, but getThumb() must return a subclass of SuperOne.
---
Michael Wentzel
Software Developer
Software As We Think - http://www.aswethink.com
mailto:[EMAIL PROTECTED]
- Punisher of those who cannot spell dumb!
RE: Java Question on Inheritance
Then this is my next problem.
I currently have getThumb() returning an Image object.
The part where I am stuck at is what to do in the toURL() method.
my mock getThumb() method currently looks something like
public Image getThumb(){
this.iValue = "/home/thumbs";
return this;
}
Well, I would imagine your toURL() method would call a method that
has a default implementation in SuperOne and was overridden in any
subclasses that needed a different implementation.
i.e.
code
public java.net.URL toURL() {
java.net.URL url = null;
if (getFilename() != null) {
url = new java.net.URL(getFilename());
}
return url;
}
/code
It depends on what manner(servlet, applet, etc...) you are going to be using
these objects where you can get additional relative file name info for the
getFilename() method to include with the value in {SuperOne}.iValue.
In addition, you might consider changing your class name. I caught
myself several times referring to java.awt.Image when you were
referring to Image class. It's always best to create unique class
names whenever possible. Maybe SuperImage or something to create
a mental correlation between this class and the class it extends.
Just a thought...
---
Michael Wentzel
Software Developer
Software As We Think - http://www.aswethink.com
mailto:[EMAIL PROTECTED]
- Punisher of those who cannot spell dumb!
Re: Java Question on Inheritance
Ryan wrote:
Then this is my next problem.
I currently have getThumb() returning an Image object.
The part where I am stuck at is what to do in the toURL() method.
my mock getThumb() method currently looks something like
public Image getThumb(){
this.iValue = "/home/thumbs";
return this;
}
Exactly what are you going to do with an Image on the server side?
A request from a browser will be for an image file in something like
.gif of .jpg format.
--
WBB - [EMAIL PROTECTED]
Java Cert mock exams http://www.lanw.com/java/javacert/
Author of Java Developer's Guide to Servlets and JSP
ISBN 0-7821-2809-2
