How to use backing store in JPanel?

Question

Below is a sketch of a class that extends JPanel. If I remove the variable "draw", the class works fine, except that the graphics drawing code is executed every time the parent window is fronted, resized, etc.
I introduced the variable "draw" hoping that the call super.paintComponent(g) would use the backing store to refresh the display. Instead, the call simply erases the panel.
How can I use the backing store?
Thanks, for your help.
public class DisplayPanel extends JPanel {
     boolean draw = true;
     public void paintComponent(Graphics g) {
         super.paintComponent(g);
         if (!draw)
               return;
          // graphics drawing code here.
         draw = false;
     }

Answer 1

Backing stores are only used on JViewpots. You will need to draw each time.