有什么办法能删掉窗口中的某个组件而不变动其他的组件吗

[asd65285]

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.Box;
public class LnFrame extends Frame implements MouseListener
{
private Frame fr;
private Color col;
private Panel panl;
private TextField username,password;
private Button sub,reset;
private Choice rdpsw,rdln;
private Box box;
public LnFrame()
{
col=Color.orange;
fr = new Frame("KTV管理员登录");
fr.setBackground(Color.LIGHT_GRAY);
fr.setUndecorated(true);
fr.setBounds(500, 300, 380, 270);
panl=new Panel();
panl.setLayout(null);
username=new TextField("请输入管理员账号",0);
username.setBounds(112,134, 188, 23);
password=new TextField("请输入管理员密码",20);
password.setEchoChar('*');
password.setBounds(112, 167, 188, 23);
sub=new Button("退出");
sub.setBackground(col);
sub.addMouseListener(this);
sub.setBounds(303, 241,70,20);
panl.add(sub);
panl.add(password);
panl.add(username);
fr.add(panl);
fr.setVisible(true);
fr.validate();
}

@Override
public void mouseClicked(MouseEvent e) {
// TODO Auto-generated method stub
System.exit(0);
}
@Override
public void mousePressed(MouseEvent e) {
// TODO Auto-generated method stub

}
@Override
public void mouseReleased(MouseEvent e) {
// TODO Auto-generated method stub

}
@Override
public void mouseEntered(MouseEvent e) {
// TODO Auto-generated method stub

}
@Override
public void mouseExited(MouseEvent e) {
// TODO Auto-generated method stub

}
public static void main(String[] args) {

LnFrame f=new LnFrame();
}
}
比如这个程序，当鼠标移动到按钮退出的时候，只有退出按钮被删掉，其他仍然正常

[asd65285]

.....没人回复啊！！