让界面居中

        Dimension screenDimension = tk.getScreenSize();   
        int screenWidth = screenDimension.width;   
        int screenHeight = screenDimension.height;   
        setLocation((screenWidth - frameWidth) / 2,   
                (screenHeight - frameHeight) / 2); 

用以上代码就可以根据屏幕的大小定位我们的界面.

eg.

import javax.swing.*;
import java.awt.*;
public class testFrame extends JFrame {
	public testFrame(){
	setTitle("居中");
	setSize(400,400);
	setVisible(true);
	setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	Toolkit tk = Toolkit.getDefaultToolkit(); 
    Dimension screenDimension = tk.getScreenSize();   
    int screenWidth = screenDimension.width;   
    int screenHeight = screenDimension.height;   
    setLocation((screenWidth - getWidth()) / 2,   
            (screenHeight - getHeight()) / 2); 
    
	}
	public static void main(String[] args){
		new testFrame();		
	}

}