If you are using an applet, just override the Paint() function. It will pass a Graphics object to the function which you can use to draw with. I know there is something for drawing a single pixel (which is SLOW) but you can simulate that with a DrawLine() function with the same beginning and end points.

If you need to draw points efficiently, there is a special type of Image which takes an array of bytes and create an image of it. If you pass the same array of the same size over and over again, I think it won''t continually create new Images, but reuse the first one.