Re: [Jsynthlib-devel] Fwd: Overriding calculateChecksum

[denis q. <dqu...@fr...>]

yes, that's why singleton is preferred to static methods.
A singleton class can use inheritance.

-- 
Denis


> That sounds right. If it's a static method there's no this pointer, so
> there would be no way to figure out which class's method to call at
> runtime. I don't know the language spec, but since Eclipse gives a
> warning whenever a static method is called through an object, I'd
> guess that all static methods are statically resolved at compile time.
> 
> 
> On Mon, 28 Feb 2005 09:25:58 -0800 (PST), Jeff Weber
> <jww...@ya...> wrote:
> 
>>--- Hiroo Hayashi <hir...@co...> wrote:
>>
>>>I can hardly believe what you wrote. If override
>>>does not work, the Java
>>>environment is useless at all.  How did you confirm
>>>it? What happen if
>>>you put print statement in your
>>>calculateChecksum(Patch,int,int,int)?
>>
>>Defies logic doesn't it? I know I have to keep
>>pinching myself. I've tested this numerous times both
>>stepping through with a debugger and using print
>>statements. Finally, I put together a really simple
>>example that demonstrates this (See below).
>>
>>What I've found out is that it appears to be happening
>>because Driver.calculateChecksum(Patch, int, int, int)
>>is defined as a static method.
>>
>>The attached example has a main class (StaticOverride)
>>along with two classes, Rectangle, which inherits from
>>Object, and Square which inherits from Rectangle. Both
>>Rectangle and Draw contain a static draw(int) method
>>that prints a message int number of times. Rectangle
>>has a non-static draw() method that calls the
>>draw(int) method. The main class, StaticOverride
>>creates an object of type Square and calls it's draw()
>>method. Because Square.draw() is commented out, it
>>calls Rectangle.draw() which in turn calls draw(int).
>>You would think that because draw(int) is overridden
>>in the Square class, that Square.draw(int) would be
>>called but nope, Rectangle.draw(int) is called
>>instead.
>>
>>If you make the draw(int) methods non-static in both
>>the Rectangle and Square classes, then it works the
>>way you'd expect and the Square.draw(int) method is
>>called instead. (At least, that's what happens on my
>>system).
>>
>>Go ahead and try it. If you get different results than
>>I did, then something's flakey either with my system
>>or my brain.
>>
>>Here's my example:
>>----------------------------
>>import java.util.*;
>>
>>public class StaticOverride {
>>
>>    public static void main (String args[]) {
>>        Square aSquare = new Square();
>>
>>        aSquare.draw();
>>    }
>>}
>>
>>class Rectangle {
>>    int nbr = 2;
>>
>>        void draw() {
>>                draw(nbr);
>>        }
>>
>>    static void draw (int num) {
>>        for (int i = 0; i < num; i++) {
>>            System.out.println("Drawing a
>>rectangle.");
>>        }
>>    }
>>}
>>
>>class Square extends Rectangle {
>>    //  void draw() {
>>    //        draw(nbr);
>>    //    }
>>
>>    static void draw (int num) {
>>        for (int i = 0; i < num; i++) {
>>            System.out.println("Drawing a square.");
>>        }
>>    }
>>}
>>
>>
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> 
> 
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