Netbeans GUI Designer & Fixed-Size Application Panels

this.mainPanel.setSize(new Dimension(800,600));
this.mainPanel.setMaximumSize(new Dimension(800,600));
this.mainPanel.setMinimumSize(new Dimension(800,600));
this.mainPanel.repaint();

protected void growBig()
  {
    int screenWidth = java.awt.Toolkit.getDefaultToolkit().getScreenSize().width;
    int screenHeight = java.awt.Toolkit.getDefaultToolkit().getScreenSize().height;
    Rectangle rectangle = getFrame().getBounds();
    rectangle.setSize(screenWidth, screenHeight);
    getFrame().setBounds(0, 0, screenWidth, screenHeight);
    getFrame().setSize(screenWidth, screenHeight);
    getFrame().doLayout();
    getFrame().validate();
    updateUI();
  }