Não consigo desenhrar string

public void drawInformation(Color back, Color font, String str, int i){
        double alpha= (100-(100*i*0.1))*0.01;
        double p=100;
        Graphics2D gr = bf8.createGraphics();
        gr.setColor(back);
        gr.setComposite(AlphaComposite.SrcOver.derive((float)alpha));
        gr.fillRect(0, 0, 140, 20);
        gr.setComposite(AlphaComposite.SrcOver.derive((float)p/100));
        Font f = new Font ("Arial", Font.PLAIN ,10);
        gr.setFont(f);
        gr.setColor(font);
        gr.drawString(str,0,0);
        gr.dispose();
        imagem7=new JLabel(new ImageIcon(bf8));
        imagem7.setLocation(0,0);
        imagem7.setSize(140,20);

    }