Desenho direto - Active Rendering --- Dúvida

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package estudandopontov;

import java.awt.Color;
import java.awt.Graphics;

/**
 *
 * @author André
 */
public class ActiveRendering extends javax.swing.JFrame {

    /**
     * Creates new form ActiveRendering
     */
    public ActiveRendering() {
        initComponents();
        setIgnoreRepaint(true);
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 580, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 500, Short.MAX_VALUE)
        );

        pack();
    }// </editor-fold>

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(ActiveRendering.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(ActiveRendering.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(ActiveRendering.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(ActiveRendering.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new ActiveRendering().setVisible(true);
            
            }
        });
    }
    // Variables declaration - do not modify
    // End of variables declaration

public void setup() {
    //Criamos a estratégia de double buffering
    createBufferStrategy(2);
    //Subtrai a decoração da janela da largura e altura máximas
    //percorridas pela bola.
    ball = new Ball(getWidth() - getInsets().left - getInsets().right, 
            getHeight() - getInsets().top - getInsets().bottom);
}


public void renderGraphics() {        
    Graphics g = getBufferStrategy().getDrawGraphics();
     
    //Criamos um contexto gráfico que não leva em conta as bordas
    Graphics g2 = g.create(getInsets().right, 
               getInsets().top, 
               getWidth() - getInsets().left, 
               getHeight() - getInsets().bottom);
    //Limpamos a tela
    g2.setColor(Color.BLACK);        
    g2.fillRect(0, 0, getWidth(), getHeight());
     
 
    ball.draw((Graphics2D) g2); //Desenhamos a bola
     
    //Liberamos os contextos criados.
    g.dispose(); 
    g2.dispose();
}
 

public void paintScreen() {
    if (!getBufferStrategy().contentsLost())
        getBufferStrategy().show();
}

}