Is there a way of determining the default sizes of Swing components without creating one (e.g. JTextField)?
However you could run a simple program which does the computation for that machine/display/desktop font setting and save the information in a file for subsequent use. Such a program may be run by the user or your application if it detects any change in machine name, display, desktop font setting.
It is alaways possible to create a dummy frame at location (-10000, -10000), add components to it and the ask for their preferredSizes etc.