What is the most elegant way to cast a variable you just received as an argument?

Question

More specifically, what's the most elegant way to cast the Graphics object in a paint() call up to a Graphics2D object?

public void paint(Graphics g) {
    // How do I convert/cast/etc the g variable to a Graphics2D object?
}

Or am I missing the point here? Is there a better way to handle this in general?

Answer 1

Graphics2D g2 = (Graphics2D)g;

There is no need to be fancy about it.

You will always receive a G2D in the paint method.

I even like to call the Graphics parameter g2 and then cast to a Graphics2D named g to make using it simpler.

Answer 2

Graphics2D g2 = Graphics2D.class.cast(g);

Answer 3

As far as I know, you can't do much in this situation. You can validate that you actually got a Graphics2D object before casting. But, as far as I know, you can get anything else anyway.

Answer 4

Personally I like

Graphics2D g2 = g as Graphics2D;
if (g2 == null)
//do stuff

But as said before, no reason to make it anymore complicated than it is :P

Answer 5

Its not directly relevant, but in Scala they recognised this "unpleasantness" - and encourage you to use pattern matching to deal with the correct class instead of a cast:

g match { 
     case Graphics2D(g2d) => //code goes here !
     case _ => Nothing //or throw exception etc
}

They actively discourage casts (there is no special cast syntax, only a method).

Not entirely relevant to you, but thought its worth noting that others are troubled by what troubles you ;)