First of all, thank you for providing this very useful software for free.
Here are some suggestions for improvements:
The visual alert (change of color) in the watchlist window could
optionally be supported by an acoustical signal.
Sometimes the data for a single stock seems to be unavailable, so
that all values are displayed as "0,00". (This has already been
mentioned in the forum.) In these cases, JStock should use at least
the old values, which could be displayed in gray, for instance.
If a stock hasn't been traded for a long time, the last price may
differ significantly from the current price. Therefore, the
calculated portfolio balance will not reflect the actual situation.
This could be avoided by using the current bid price instead of the
last price for calculating the balance.
Sound alert is already supported : http://www.jstock.org/features.html
JStock Android is having such scheme. When there is no internet connection, old value will be shown, with status bar displayed date of the data. But Desktop doesn't have such scheme yet.
By definition, the valuation of your stock, is based on the last actual traded price. So, this behavior is correct. Bid price doesn't reflect the actual market value of a stock.
(1.) Doesn't work for the watchlist window. I meant the temporary change of background color when there is a difference between incoming and present data. An additional acoustical alert would be useful here.
(3.) If a stock hasn't been traded for weeks, the last price may be completely irrelevant. In such cases, using the current bid price would lead to more realistic results.