Why the drawPolygon method in Graphics Class abstract and I can still use it

In Graphics Class, there is an abstract method defined as

public abstract void drawPolygon(int[] xPoints, int[] yPoints, int nPoints)

Why do I still be able to use the method directly in my开发者_如何学Python code?

EDIT: In the Official java documentation, the only Direct Known Subclasses of Graphics is Graphics2D, which doesn't implement the method, and doesn't have any Direct Known Subclasses.

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Yes, you can still use it because you are not actually using the abstract class Graphics in your code. Your application will be using a concrete subclass of Graphics, which is passed to methods such as paintComponent(Graphics). This concrete subclass will have drawPolygon(int[], int[], int) implemented.

This lesson on painting in Swing may help provide more details on how these methods work. The article Painting in AWT and Swing will also be useful.