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);
     }
 }