JAVA Swing---讓Frame顯示於螢幕中央

要讓Frame顯示於螢幕中央有兩種方式:
Case1.
import java.awt.*;

JFrame f = new JFrame();
Dimension dim = Toolkit().getDefaultToolkit().getScreenSize();
f.setLocation(dim.width/2-f.getWidth()/2, dim.height/2-f.getHeight()/2);

Case2.
import java.awt.*;

JFrame f = new JFrame();
f.setLocationRelativeTo(null);

reference: http://java.sun.com/j2se/1.4.2/docs/api/java/awt/Window.html#setLocationRelativeTo%28java.awt.Component%29