Re: [Jsynthlib-devel] Fwd: Overriding calculateChecksum

[Rib R. <ri...@gm...>]

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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