SwingUtilities.paintComponent() takes a Component argument, so it is possible (though a pretty bad idea) for a java program to pass a heavyweight Component to paintComponent(). This was in part the cause for bug 4321847. With Kestrel (post build Y i.e. including the fix for 4321847), the following code throws a NullPointerException. With 1.4, the Button is painted over with the Frame's background color.

import javax.swing.*;
import java.awt.*;

public class otherTests {

    public static void main(String argv[]) {
        Button comp = new Button("Some nonsense");
        Frame pn = new Frame();
        pn.add(comp);
        pn.setSize(200,100);
        pn.setVisible(true);

        Rectangle bounds = comp.getBounds();
        comp.getGraphics().create(bounds.x, bounds.y, bounds.width,
                                                bounds.height).getClipBounds();

        SwingUtilities.paintComponent(comp.getGraphics(), comp, pn,
                     bounds.x, bounds.y, bounds.width, bounds.height);
        System.out.println("OKAY");
    }

}