java登陆界面

package liyu;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

class login extends JPanel{
static final int WIDTH=300;
static final int HEIGHT=300;
JFrame loginframe;
public void add(Component c,GridBagConstraints constraints,int x,int y,int w,int h){
constraints.gridx=x;
constraints.gridy=y;
constraints.gridwidth=w;
constraints.gridheight=h;
add(c,constraints);
}
login(){
final JFrame loginframe=new JFrame("学生登录");
loginframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
GridBagLayout lay=new GridBagLayout();
setLayout(lay);
loginframe.add(this,BorderLayout.WEST);
loginframe.setSize(WIDTH,HEIGHT);
Toolkit kit=Toolkit.getDefaultToolkit();
Dimension screenSize=kit.getScreenSize();
int width=screenSize.width;
int height=screenSize.height;
int x=(width-WIDTH)/2;
int y=(height-HEIGHT)/2;