I'm trying to use a scrollpane with some components which size changes
during the execution of the program.

If you initialize a JScrollPane with a component which is initialy smaller
than the scrollpane, and if this component becomes bigger, then the
scrollbars of the scrollpane remain hidden.
This problem does not exist if the component is initialy bigger than the
scrollpane and become smaller (the scrollbars disappear and appear again
as soon as the component is bigger than the scrollpane).

I'm using Swing 1.0.2.

You'll find in the attachment a small program which illustrates the
problem.