Java: Override a method from grandparent

Question

I have an abstract class A, and an abstract class B inheriting A. Then, I have a class C(not abstract) that inherits B.

I need to override some methods declared abstract in A, and not implemented in B to be implemented in C.

But when I try to do this, and add an Override annotation on top of my method, it says its not valid as that method does not exist in the parent.

How can I do this?

Code with signatures:

public abstract class A {

abstract protected EntityType getEntityType();
abstract protected ActionResponse doProcessing();
}

public abstract class B extends A {
   @Override
   EntityType getEntityType() {
     ....
    ...
    }
}

public class C extends B {
     @Override
     ActionResponse doProcessing() {
     ...
     ..
    }
}

make sure the signature of the overridden method matches the overriding method. and make sure this method in class A is visible to class C — Eran, Dec 19 '14 at 11:22
I tried to put your words into code above to make it easier for others to follow. — Mr. Polywhirl, Dec 19 '14 at 11:25

Bruce · Answer 1 · 2014-12-19T12:07:06.617

1

Access Modifier of the Sub class can't weaker than it's Super Class. It is better to change the Access Modifier of the sub classes to protected from default

edited Dec 19 '14 at 12:07

answered Dec 19 '14 at 11:27

Bruce

8,609
8
54
83

@OliverCharlesworth [says otherwise...](http://stackoverflow.com/questions/14132285/java-methods-override-vs-abstract#comment19566511_14132285) It may just dependent on the version of Java. This may not work in version 1.5. – Mr. Polywhirl Dec 19 '14 at 11:33
There was a typo in my code earlier, check it out now – Bulbasaur Dec 19 '14 at 11:52
1

you put weaker access modifier in your sub class did you check that – Bruce Dec 19 '14 at 12:03

score 0 · Answer 2 · answered Dec 19 '14 at 11:39

0

A:

public abstract class A {
    public abstract D getClassD();
}

B:

public abstract class B extends A{
}

D:

public class D {
}

And C:

 public class C extends B {
    D d = new D();

    @Override
    public D getClassD() {
        return this.d;
    }
}

It's correct. You cannot create class C without override method getClassD().

Please add field and initialize it. If you use Eclipse you can change in setting that IDE should put @Override or not

answered Dec 19 '14 at 11:39

Roman Kazanovskyi

3,370
1
21
22

This is what I did, it doesn't work. It says: : method does not override or implement a method from a supertype(after adding override annotation) – Bulbasaur Dec 19 '14 at 11:56

score 0 · Answer 3 · answered Dec 19 '14 at 12:19

Your scenario works just fine in JavaSE 1.7. What version of java are you using?

public abstract class A {
    protected abstract Integer getMyInt();
    protected abstract String getMyString(); 
}

public abstract class B extends A {
    @Override
    protected String getMyString(){
        return "The answer is";
    }
}

public class C extends B {
    @Override
    protected Integer getMyInt() {
        return 42;
    }
}

public class Test {
    public static void main(String[] args) {
        C c = new C();
        System.out.println(c.getMyString() + " " + c.getMyInt());
    }
}

score 0 · Answer 4 · answered Jun 02 '20 at 08:49

0

If you could access the grandparent directly you would create a dependency on the implementation of the father, and this would violate encapsulation.

answered Jun 02 '20 at 08:49

Tal

11
4

Java: Override a method from grandparent

4 Answers4