In Windows and solaris
**********************
When parent frame is hidden, currently active dialog is also hidden. But when the parent frame is made visible again, dialog is not visible and it is still hidden. This holds good for Modal, modeless and file dialogs.
                

Here a separate thread starts before the modal dialog is made visible, so that
we can make the parent frame hidden in a separate thread. Thread which executes
ModalDialog.setVisible() waits till the modal dialog is disposed and statements
following setVisible() will not be executed until the modal dialog is disposed.
So a separate thread is started before dialog.setVisible() to perform the hiding
and showing functions of the parent frame.

When the parent frame is hidden dialog is also hidden and when parent frame is
shown dialog is not shown and it still remains hidden.


How to reproduce the bug?---->
Run this sample code. You would see a frame with 3 buttons. First click the
Modal dialog button and wait until the message "Testing over for this dialog
type" appears in the command prompt. Observe the behaviour and check whether
the respective dialog is visible when the above said message appears in the
command prompt. Repeat this for all the dialog types by clicking the
appropriate buttons.