Accessing Java default methods in a subinterface or implementation class

Question

I understand if a class overrides a default method, you can access the default method in the following manner

interface IFoo {
    default void bar() {}
}

class MyClass implements IFoo {
    void bar() {}
    void ifoobar() {
        IFoo.super.bar();
    }
}

But what about the case where an interface overrides a default method? Is the parent method available in any way?

interface IFoo {
    default void bar() {}
}

interface ISubFoo extends IFoo {
    // is IFoo.bar available anywhere in here?
    default void bar {}
} 

class MyClass implements ISubFoo {
    // is IFoo.bar available anywhere in here too?

    public static void main(String[] args) {
        MyClass mc = new MyClass();
        mc.bar(); // calls ISubFoo.bar
    }
}

The verbiage Java uses for default methods is similar to that for classes, otherwise it's confusing/misleading. Subinterfaces "inherit" default methods, and can "overwrite" them. So it seems IFoo.bar should be accessible somewhere.

No, there is no super.super in Java. You can never access a method that was overridden in the parent, regardless of wether it's a class or a default method on an interface. — Boris the Spider
– Boris the Spider, Commented Oct 8, 2014 at 15:05

Erwin de Gier · Accepted Answer · 2015-03-19 12:12:49Z

2

You can go one level up, so the IFoo.bar() is available in ISubFoo with IFoo.super.bar().

interface IFoo {
    default void bar() {}
}

interface ISubFoo extends IFoo {
    // is IFoo.bar available anywhere in here?
    // Yes it is
    default void bar {
        IFoo.super.bar()
    }
} 

class MyClass implements ISubFoo {
    // is IFoo.bar available anywhere in here too?
    // Not it is not

    public static void main(String[] args) {
        MyClass mc = new MyClass();
        mc.bar(); // calls ISubFoo.bar
    }
}

answered Mar 19, 2015 at 12:12

Erwin de Gier

6627 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Accessing Java default methods in a subinterface or implementation class

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related