in Swing (by Robinson) and in this sun tutorial its claimed:
If you specify a Frame or Dialog, then the Dialog will appear over the center of the Frame (...). If you specify a component inside a Frame, then the Dialog will appear over the center of that component (...). If you specify null, then the look and feel will pick an appropriate position for the dialog — generally the center of the screen (...).
the example i show bellow infirms that:
frame isnt centered - either using new JFrame() or null the dialog pops up centered relative to screen
frame is centered - in both cases dialog appears centered relative to screen, as above
my conclusion: dialog allways centers itself relative to screen
what am i missing here?
Check out Window's setLocationRelativeTo method. If you pass null as its argument it will center the window (JFrame is a Window subclass) on the screen taking into account things like the task bar etc.