java 使用ActionListener监控

package test;

import java.awt.Font;
import java.awt.GridLayout;
import java.awt.LayoutManager;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
//import java.util.EmptyStackException;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

class ActionHandle{
    private JFrame f=new JFrame("Welcome to use Login!");
    private JButton but=new JButton("显示");
    private JLabel lab=new JLabel();
    private JTextField text=new JTextField(10);
    private JPanel pan=new JPanel();
    public ActionHandle(){
        Font fnt=new Font("Serief",Font.ITALIC+Font.BOLD,28);
        lab.setFont(fnt);
        lab.setText("等待用户输入信息！");
        but.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if(arg0.getSource()==but){
                    lab.setText(text.getText());
                }
            }
        });
        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent arg0){
                System.exit(1);
            }
        });
        f.setLayout(new GridLayout(2,1));
        pan.setLayout(new GridLayout(1,2));
        pan.add(text);
        pan.add(but);
        f.add(pan);
        f.add(lab);
        f.pack();
        f.setVisible(true);
    }
}
public class test {
    public static void main(String[] args) {
        
        new ActionHandle();
    }

}