Multiple extending

[PlasmaDragon]

I have a class, let's call it "x". I have another class, y, which
extends x. Then I have a class z which extends y. There is a
function in y (but not in x) which I have overridden in z. But when I
try to run the program, it uses the version of the function in y! I
have heard that java doesn't support multiple inheritance, so could
this be the problem?

So basicall: is there a rule in java which I am violating by trying to
have a class extend a class extending a class? And if so, what can I
do to work around it?

[Chris]

Re: Multiple extending

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PlasmaDragon wrote:
[color=blue]
> I have a class, let's call it "x". I have another class, y, which
> extends x. Then I have a class z which extends y. There is a
> function in y (but not in x) which I have overridden in z. But when
> I
> try to run the program, it uses the version of the function in y! I
> have heard that java doesn't support multiple inheritance, so could
> this be the problem?
>
> So basicall: is there a rule in java which I am violating by trying
> to
> have a class extend a class extending a class? And if so, what can
> I do to work around it?[/color]

Hi,
No rules violated here, and this doesn't actually have to do with
multiple inheritance. Multiple inheritance means one class cannot
*directly* extend two classes. However, I'm not sure where your
problem comes from. Examine the following code, of my design:

- --- X.java ---
public class X {
public X() {
}
}


- --- Y.java ---
public class Y extends X {
public Y() {
super();
}

public void doSomething() {
System.out.prin tln("Something in Y.");
}
}


- --- Z.java ---
public class Z extends Y {
public Z() {
super();
}

public void doSomething() {
System.out.prin tln("Something in Z.");
}

public static void main(final String[] args) {
Y y;
Z z;

y = new Y();
y.doSomething() ;

z = new Z();
z.doSomething() ;

y = z;
y.doSomething() ;
}
}


- --- END OF FILES ---

Compiling the above files, then running as "java Z", produced the
expected output of:

Something in Y.
Something in Z.
Something in Z.

- --
Chris
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[PlasmaDragon]

Re: Multiple extending

I found the problem. The function I overrode in Z was called in Y by
another function, so it used the Y version. So I copied the caller
function into Z and the problem is solved.