Java 创建一个窗口，使其启动时位于屏幕中间

 import java.awt.Toolkit;

 import javax.swing.JFrame;

 public class WindowInTheMiddle extends JFrame {

     public static void main(String[] args) {

         WindowInTheMiddle window = new WindowInTheMiddle();

         window.launchFrame();

     }

     public void launchFrame() {

         // The width & Height of the window

         final int formWidth = 500;

         final int formHeight = 500;

         // The width & Height of the screen

         int screenWidth = (int)Toolkit.getDefaultToolkit().getScreenSize().getWidth();

         int screenHeight = (int)Toolkit.getDefaultToolkit().getScreenSize().getHeight();

         // Set title, size, location & visible

         this.setTitle("Hello World! I'm coming!");

         this.setSize(formWidth, formHeight);

         this.setLocation((screenWidth-formWidth)/2, (screenHeight-formHeight)/2);

         this.setVisible(true);

     }

 }