[ajug-members] casting

[Wilson, Jeff]

You absolutely can only cast up or down an inheritance hierarchy OR cast
an object to any interface that it or its parent classes implements. You
cannot cast, in your example, a Subtractor object to be an Adder object.
That makes no sense in an object oriented language.

Casting doesn't change the type of the object, it just narrows the array
of types that the object already implements.

+jeff (MJW)
---

"The only way to deal with bureaucrats is with stealth and sudden
violence."
      -- B. Boutros-Ghali

---------------------------------------------
M. Jeff Wilson, Lead Member Technical Staff
AT&T Services, Inc.
Operations & Service Dev
jw9615 at att.com 
+1 404.499.7235
> -----Original Message-----
> From: 521 [mailto:521 at ofig.org]
> Sent: Tuesday, July 01, 2008 4:12 PM
> To: ajug-members at ajug.org
> Subject: [ajug-members] casting
> 
> can I only cast up/down a hierarchy?
> 
> per below, what would the syntax be in order for a 'Subtractor' object
use
> the Adders classes' showadder method?  would it be like this- to cast
> Adder 'type' on the sub object- that is, in order to get to an Adder's
> method? (Adder)sub.showadder
> 
> 
> [code]
> public class ProgramDisplayer {
> 	public static void main(String args[]) {
> 		System.out.println("Hi!");
> 
> 		Adder add = new Adder();
> 		add.showadder();
> 
> 		Subtractor sub = new Subtractor();
> 		sub.showsubtractor();
> 	}
> }
> [/code]
> [code]
> public class Adder{
> 	public void showadder() {
> 		int low = 0;int high = 9;int count=low;
> 		while(count<high){System.out.println(count);count++;}
> 	}
> }
> [/code]
> [code]
> public class Subtractor {
> 	public void showsubtractor() {
> 		int low = -10;int high = 0;int count=high;
> 		while(count>low){System.out.println(count);count--;}
> 	}
> }
> [/code]
> 
> Thanks,
> 
> Barclay
> 
> 
> 
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