Question about drawing animations in Java (SWT)

[instop]

Hello, i've got a question about drawing animations in Java (SWT).
I try to draw an animation of some process.
When i use canvas.redraw() it seems like program firstly erases everything that has been drawn and then draws again.
My program draws about 1000 of rectangles per time step so animation doesn't looks smooth - it blinks all the time and I can't avoid drawing that many rectangles.
Is there a way to make it look smoother (for example to paint new objects over old ones, without erasing them)?
I won't paste code, it's rather large.
Can you help me please?

[instop]

The solution for flickering when doing custom painting is to use double buffering. The SWT Canvas object has built-in double-buffering, use it by adding the flag to the styles in the constructor:

Canvas myCanvas = new Canvas (parentComposite, SWT.DOUBLE_BUFFERED);

Thanks to BenG