Centering a JFrame

The old way to center a JFrame was to use the default java.awt.Toolkit object and call getScreenSize then explicitly call setLocation on the JFrame.

Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
  int x = frame.getSize().width;
  int y = frame.getSize().height;

Since 1.4 the better way is to call setLocationRelativeTo(null). This will center the JFrame. If you supply a Component object to the function, and the component is say on the left side of the screen, your JFrame will appear to the right of the screen.