public class Background extends JPanel{
@Override
public void paint(Graphics g) {
Image planoDeFundo = Toolkit.getDefaultToolkit().createImage("back.jpg");
super.paint(g);
int x = (this.getWidth() - planoDeFundo.getWidth(null)) / 2;
int y = (this.getHeight() - planoDeFundo.getHeight(null)) / 2;
g.drawImage(planoDeFundo, 0, 0, this );
}
}
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AGORA DEU CERTO!
DECLAREI UMA URL SEPARADA PRA DEPOIS POR COMO PARAMETRO!
URL url = getClass().getResource("back.jpg");
Image planoDeFundo = Toolkit.getDefaultToolkit().getImage(url);