CreateImage(int, int) problem -- or..?

Question

I'm trying to get a program double buffered, and have followed the structure for doing so provided by Sun. However, the program does not work correctly.
Problem #1: I have to "manually" refresh the JFrame (put it behind a window, then bring it back to the foreground), and everything seems to work correctly.
Problem #2: When the program first starts, I get 2 NPE's.
Note: Both of these problems usually occur. Rarely, the entire thing runs perfectly with no problems at all.
Here is how the code is structured:
Graphics offScreen;
Image offScreenImage;
public void paint(Graphics screen)
update(screen);
public void update(Graphics toPaint)
if( offScreenImage == null )
offScreenImage = createImage(640, 480);     
offScreen = offScreenImage.getGraphics();
setBackground(Color.gray);          
board.draw(offScreen);
toPaint.drawImage(offScreenImage, 0, 0, null);     
} //end draw()
Also, the draw(Graphics) method from the board instance is:
public void draw(Graphics offScreen)
offScreen.drawImage(testImage, 25, 25, null);
What could be causing these problems? Is there anything special that needs to be done if I'm using separate object files to draw? The NPE's are always flagged at this line:
     board.draw(offScreen);
Any suggestions would be GREATLY appreciated.

Answer 1

problem #1: Try moving the initializing code from update to paint or make paint to call update. Paint is the method that is called first to paint the component, update is called to repaint it.
problem #2: "board.draw(offScreen);" can cause a NPE if a) board is null or b) offScreen is null. Which one is it?
Also, in swing you should override the paintComponent-method instead of paint. (And aren't swing components double buffered by default? I'm not sure about that...)