How to access a method from extending class in extended class?

Question

I want to use/call a method inside EdumateSuperClass that I created in Navigation class. Is that possible? Anything I tried didn't work.

public abstract class EdumateSuperClass extends ScriptSuperClass

public abstract class Navigation extends EdumateSuperClass

• super.clickNewButton(); --> The method clickNewButton() is undefined for the type ScriptSuperClass

PS Please update the title if necessary. Not sure if I used the right terminology.

Answer 1

You have to declare the method as abstract in the using class (or its parent classes), and implement it in the child class:

public abstract class EdumateSuperClass {
    protected abstract void childMethod(String message);

    public void callChildMethod() {
        childMethod("hello");
    }
}

public abstract class Navigation extends EdumateSuperClass {
    protected void childMethod(String message) {
        System.out.println(message);
    }
}

Answer 2

You can't use super to call a method of Navigation from inside EdumateSuperClass .

EdumateSuperClass is the superclass of Navigation .

Your hierarchy is: ScriptSuperClass -> EdumateSuperClass -> Navigation , where -> indicates "base class of" or "super class of".

Navigation can use super.X() to call concrete methods of EdumateSuperClass , not vice versa.

When you're doing super.clickNewButton() from inside EdumateSuperClass , it's trying to call the method clickNewButton from inside of the base class ScriptSuperClass . This method is undefined for the class ScriptSuperClass and therefore that is why you get that specific error.

EDIT: If you wanted, you could have EdumateSuperClass remain an abstract class which declares an abstract method abstractMethod() and Navigation be a concrete class that defines a concrete implementation of this method.

You still can't use super from EdumateSuperClass to call this method inside Navigation , however this will allow you to use EdumateSuperClass as basically an interface when grouping objects.

ie. You could have an array of EdumateSuperClass , which means that this array can hold references of concrete class objects derived/extended from EdumateSuperClass . For these classes to be concrete they must define abstractMethod() . From there you can store Navigation objects in that array and call abstractMethod() from any element in that array.

However, that doesn't mean you're calling abstractMethod() from inside EdumateSuperClass , it'll still be a Navigation object that will contain the definition of abstractMethod() and be calling that from itself. I don't know if that makes it any clearer or not.

Read up on polymorphism .