Swing Advice Needed

Been teaching myself Java in my spare time, and decided to one day try a little swing gui programming. So I wrote this little program to display a hello world JFrame. It displayed this tiny dialog in the upper left corner of my monitor. Got a little curious and decided to try placing the dialog in the center of the screen and set the frame's dimensions to half my screen size. I could not get it just right using only the swing functionality, and upon browsing the web found samples to do this and they all invoked functionality from AWT. I realize that Swing is derived from AWT but is it considered good practise to make calls to a toolkit from the one that is intended to be its replacement? Or is it okay to call AWT for functionality that does not actually render the gui but rather to get screen size or other information, and use that information to supply swing functions with the parameters needed to draw the gui? I hope that makes sense.