Why call super() in a constructor?

java superclass
mark picture mark · May 9, 2012 · Viewed 118.7k times · Source

I'm dealing with a class which extends JFrame.

It's not my code and it makes a call to super before it begins constructing the GUI. I'm wondering why this is done since I've always just accessed the methods of the superclass without having to call super();

Answer

AerandiR picture AerandiR · May 9, 2012

There is an implicit call to super() with no arguments for all classes that have a parent - which is every user defined class in Java - so calling it explicitly is usually not required. However, you may use the call to super() with arguments if the parent's constructor takes parameters, and you wish to specify them. Moreover, if the parent's constructor takes parameters, and it has no default parameter-less constructor, you will need to call super() with argument(s).

An example, where the explicit call to super() gives you some extra control over the title of the frame:

class MyFrame extends JFrame
{
    public MyFrame() {
        super("My Window Title");
        ...
    }
}

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