这个我当然知道好不好,就是不行啊

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

import java.awt.event.*;
public class Test extends JFrame implements ActionListener
{
JPanel panel=new JPanel();

Test()
{
Container con=getContentPane();
con.setLayout(new FlowLayout(FlowLayout.LEFT));
panel.setBackground(Color.white);
con.add(panel);

setSize(400,300);
setVisible(true);
}
public void actionPerformed(ActionEvent e)
{

}

public static void main(String[] args)
{
Test ap=new Test();
ap.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}