extend a class and make members private

Programming Questions

clankill3r

extend a class and make members private

in Programming Questions • 1 year ago

I basically need a PVector, however i don't want people to be able to set the x, y or z directly like p.x = 10;

Instead of that i want them to force to use p.setPosX(10);

But i still like that the other methods of PVector are still present.

Now i could copy all the code from PVector and make x, y, and z private instead of public, this might be the easiest way.

If i use this:

class CVector extends PVector {
private float x;
private float y;
private float z;
CVector(float x, float y, float z) {
super(x, y, z);
}
}

Then i still can use:

CVector cv;
void setup() {
smooth();
cv = new CVector(50, 50, 0);
ellipse(cv.x, cv.y, 5, 5);
}

Only the ellipse is drawn at 0, 0 instead of 50, 50.

Is it possible in a way to make x, y and z private?

And the reason it doesn't work now, is that cause everything is a inner class in processing?

If it is it is no problem since i have to use it in java anyway, i just like testing out in processing.

Replies(5)

calsign

Re: extend a class and make members private

1 year ago

Okay... in this scenario, you've got something pretty confusing going on.

In Java, you simply cannot make a public variable private in an extending class. So here, you are creating three completely different variables called x, y, and z. Now, when you call CVector's constructor, that will, in turn, call PVector's constructor, which will set PVector's x, y, and z variables to be the given parameters: 50, 50, and 0. Then, when you try to access the CVector's x, y, and z variables, they have not been set to anything! The reason that you can access them in the first place is, yes, because they are in an inner class.

As you said yourself, it would be easier to copy PVector's source and simply make the variables private.

clankill3r

Re: extend a class and make members private

1 year ago

thanks.

In Java, you simply cannot make a public variable private in an extending class.

And is there no other way then copy paste?

(which i will do now i guess)

calsign

Re: extend a class and make members private

1 year ago

You could try creating a wrapper class (a class that contains a PVector object to which you apply all functionality)...

clankill3r

Re: extend a class and make members private

1 year ago

the java examples i find look complex, it's just as simple as this right:

class CVector {
private PVector pos = new PVector();
CVector() { }
CVector(float x, float y, float z) {
pos = new PVector(x, y, z);
}
// wrappers:
void setPos(float x, float y, float z) {
pos.setPos(x, y, z);
}
// etc.
}

calsign

Re: extend a class and make members private

1 year ago

Yes... that would have to be declared in a separate Java file (not nested) and it's still about as redundant as the first method, i.e. duplicating PVector and privatizing its variables.

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