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

public class aa {
    public static void main(String[] arge){
        JButton b=new JButton("zhang");
        JFrame f=new JFrame("Test");
        Mon bn=new Mon();
        b.addActionListener(bn);
        f.add(b,BorderLayout.CENTER);
        f.pack();
        f.setVisible(true);
        
            
            
        }
    class Mon implements Actionlistener{
        public void actionPerformed(ActionEvent e){
            System.out.println("li");
        }
    }
    }

}

Actionlistener写错了ActionListener