CODEWITHSUNDEEP
javainheritance
Daniel
Daniel

Reputation: 855

Inheritance and method scope in Java

In the following example pseudocode:

public class MyPanel extends JPanel {
    public void reset() {
        this.clear();
        clear();
    }
    public void clear() { System.out.println("FAIL"); }
};

public class MySpecialPanel extends MyPanel {
    public void clear() { System.out.println("Hello, world"); }
};

When calling (new MySpecialPanel()).reset() shouldn't both this.clear() and clear() resolve in the same scope? Is there any difference between this.clear() and clear()?

Upvotes: 0

Views: 741

Answers (4)

ring bearer
ring bearer

Reputation: 20783

Stating the obvious as many have already responded - when you call clear() on an object, that object is in scope; when you use this you are referring to that same object in context.

Upvotes: 0

francesco.s
francesco.s

Reputation: 306

in your code:

public void reset() {
    this.clear();
    clear();
}

both this.clear() and clear() are the same.

this is a keyword for setting the scope of the call inside the class itself super sets the scope to the class itself and the superclass

Upvotes: 0

Kal
Kal

Reputation: 24910

There is no difference between this.clear() and clear().

You have a MySpecialPanel object and the clear() method on that object is called twice. To call the superclass's clear, you must use super.clear()

So, you do something like this --

public void reset() {
        clear();
        super.clear();
}

Upvotes: 1

Jeff Foster
Jeff Foster

Reputation: 44706

public void reset() {
    this.clear();
    clear();
}

In the code above, that calls the same method twice. There is no difference between clear() and this.clear().

You can explicitly call the superclasses method with super.clear().

Upvotes: 5

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