CODEWITHSUNDEEP
javainheritanceabstract-classabstract
Amol Ghotankar
Amol Ghotankar

Reputation: 2094

How to call over-ridden abstract class methods

I have scenario like

Here is the abstract class

    abstract class A
    {
            public void add()
            {
                    //do something
            }
    }

Here is the class that extends above abstract class

    class B extends A
    {
            @Override
            public void add()
            {
                    //do something else
            }
    }

Here is the class in which I want to call both the add methods

    class C
    {
            A a = new B();

            // Calls B's add method

            a.add();

            // Call A's add method ???
    }

How to call A's add method???

Upvotes: 0

Views: 4417

Answers (6)

Amol Ghotankar
Amol Ghotankar

Reputation: 2094

I got what i want but in different way here it is how ---

    class D extends A
    {
            public add()
            {
                    //Log here..........
                    super.add();
            }
    }

This will help me not to force B to call default implementation of A by avoiding super.add();

As we have over-ridden it to change functionality.

    class C
    {
            A a = new B();
            // Call B's Add method
            a.add();

            a = new D();
            // Call A's Add method via D
            a.add();
    }

I think there is no other better way than this :)

Upvotes: 0

c'quet
c'quet

Reputation: 345

class B extends A
{
//over ride method
public add()
{
    //do something else
}

public add2()
{
    super.add();
}
}


class C {
A a = new B();

// Calls B's add method
a.add();

// Call A's add method
a.add2();
}

Upvotes: 1

Ravi Bhatt
Ravi Bhatt

Reputation: 3163

As explained above by various people, you can't. If we try and understand as to what you want to achieve, i guess what you need is an interface and two classes.

interface AddInterface {
 public void add();
}

class A implements AddInterface {
//your abstract class' version of add goes here
}

class B implements AddInterface {
//your other add definition.
}

You end up replacing references to A with AddInterface. Again, it all depends on what you want to achieve.

Upvotes: 1

Jon Skeet
Jon Skeet

Reputation: 1500725

You can't. That's the whole point of polymorphism and encapsulation - you've created an instance of B, so B gets to decide what add means. Maybe B is trying to enforce some business rules about when you can call add for example - it would be useless if you could bypass those rules and call A.add() directly on an instance of B. The implementation of B.add() can decide when and whether to call super.add(), but code outside B doesn't get to make that decision.

Upvotes: 10

Kane
Kane

Reputation: 4157

You're looking for super.

class B extends A
{
        //over ride method
        public add()
        {
                super.add();
                //do something else
        }
}

Upvotes: 1

JB Nizet
JB Nizet

Reputation: 691755

You can't, because it would break polymorphism. If B overrides A's add method, it's because it must add in another way to satify its contract. Not doing it the way it needs to would break B's invariants, and probably also A's invariants.

Upvotes: 1

Related Questions