Making an overriden method's super refer to the superclasss super

Question

I know the title might sound a bit weird, but that's exactly what I'm willing to do. Simply explained: Class A is a sub-class of class B, and class B is also a sub-class of class C.

Now, all those classes contain the method m(). In my A class, the only one I have access to, as the others are only available at runtime, I override the B class's m() method. However, the m() method of the B class contains a call to the m() method of it's own superclass (that is C), and, although I made some modifications to it, I eventually also have to call that method.

I have searched for a while and I've heard that in similar situations this would be impossible as it would "break encapsulation", and I really understand why. However, in my case, I'm doing it all inside an overriden method, so is there any way I can actually make it so it would work this way? Thanks!

EDIT: Ahm, I think I didn't explain quiet well. I'm only overriding the method from the B class in my C class. From there, inside my method in the C class, I need to call the m() method not of the B class (which would work for super.m()) but for the C class.

Here's my actual code if it might help:

    @Override
public void m() {

    if(this.au() && this.getGoalTarget() != null && this.vehicle instanceof EntityChicken) {
        ((EntityInsentient) this.vehicle).getNavigation().a(this.getNavigation().j(), 1.5D);
    }

    try {
        ((EntityMonster) this.getClass().getSuperclass().getSuperclass().getConstructor(World.class).newInstance(this.world)).m();
    }catch(InstantiationException | IllegalAccessException | NoSuchMethodException | InvocationTargetException e){
        e.printStackTrace();
    }

}

You said your class B method already invokes super (C) method. What else do you want? — Vishal, May 29 '16 at 12:18
This all sounds a little confusing, so `A extends B` which extends `C` - fairly enough; and the method `m()` in class `B` has something like `super.m()` - which calls method `m()` of class `C` - I don't understand what you say the problem is here? Even if you override a method of the base class (`C.m()`), nothing stops you from calling that method using `super.m()` from the child (class `B`) in your case. — ishmaelMakitla, May 29 '16 at 12:22
Ahm, I think I didn't explain quiet well. I'm only overriding the method from the B class in my C class. From there, inside my method in the C class, I need to call the m() method not of the B class (which would work for super.m()) but for the C class. — dadus33, May 29 '16 at 12:26
Your edit seems contradictory. You have a `C` base class, which is extended by `B`, and finally you have `A` that extends `B`. From general to particular, `C -> B -> A`. But then, in your edit, you say you are overriding method `m()` in `C`, which doesn't make sense since it's the base class. Please clarify. — fps, May 29 '16 at 12:46
@FedericoPeraltaSchaffner No, I'm saying that, from class C, I am overriding the m() method in class B. — dadus33, May 29 '16 at 12:49
So, your hierarchy is `A -> B -> C`, where `A` is the base class and `C` is the most particular one, and you only have access to `C`. Is this right? — fps, May 29 '16 at 12:51
why dont you try simple functional interface with default method thing , make two interfaces with each method and implement both ,and use it by lambada , keep it simple — bananas, May 29 '16 at 14:22
@holidayCoder I don't understand what uou mean lol. You should keep in mind I'm kinda new to Java, I have no idea what lambda is. — dadus33, May 29 '16 at 14:56

score 2 · Answer 1 · answered May 29 '16 at 12:59

If you can't use inheritance, then you should give the decorator pattern a chance.

In the motivation section:

...sometimes (e.g., using external frameworks) it is not possible, legal, or convenient to modify the base class.

In your case, you could use the decorator pattern to add functionality to the C class (the class that inherits from B):

class A {
    public void m() {
        System.out.println("A");
    }
}

class B extends A {
    public void m() {
        System.out.println("B");
    }
}

class C extends B {

    private final A base;

    public C(A base) { // pass other needed arguments
        this.base = base;
    }

    public void m() {
        this.base.m(); // instead of super.m()
        System.out.println("C");
    }
}

You'd need to instantiate C as follows:

A base = new A();
C c = new C(base);

And then:

c.m();

Which should print:

A
C

Unfortunately, I can't do that. Maybe I should have explained it better the first time... I'm using Bukkit, and what I'm actually trying to do is to create a custom entity which aims to replace the default one. While the class for the default one is still there, I tell Bukkit to just use my class instead of that one. Also, my class inherits all the behaviour of the default class, but it adds something to it. Anyways, the thing is, I'm not the one who instantiates my class, Bukkit is. And it can only instantiate it with the normal argument of the default Zombie class (world)... — dadus33, May 29 '16 at 13:08

wake-0 · Answer 2 · 2016-05-29T12:29:11.527

0

Do you want to call it this way?

public class C {

    public void m() throws IllegalAccessException, InstantiationException {
        System.out.println("C");
    }
}

public class B extends C {
    @Override
    public void m() throws IllegalAccessException, InstantiationException {
        super.m();
        System.out.println("B");
    }
}

public class A extends B {
    @Override
    public void m() throws IllegalAccessException, InstantiationException {
        ((C) this.getClass().getSuperclass().getSuperclass().newInstance()).m();
        System.out.println("A");
    }
}

edited May 29 '16 at 12:29

answered May 29 '16 at 12:26

wake-0

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Hmm, let me see, I'll check if it works right now, but yes, that's what I want to do in theory. Never tough of using reflection though. – dadus33 May 29 '16 at 12:28
Ahm, unfortunately, it doesn't work in my case. I get an Instantiationexception: http://hastebin.com/secepakexo.avrasm – dadus33 May 29 '16 at 12:38
Do you support a default constructor? – wake-0 May 29 '16 at 12:39
Otherwise you maybe need to use an `Activator`. See [activator](http://stackoverflow.com/questions/7598088/purpose-of-activator-createinstance-with-example) – wake-0 May 29 '16 at 12:40
As you can see in my last comment I'm not using no args constructor, but I edited that my own. That still throws the exception... – dadus33 May 29 '16 at 12:44

Making an overriden method's super refer to the superclasss super

2 Answers2