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

public class Demo1 extends JFrame implements ActionListener {
    
    JButton btn  = new JButton("方法 1");
    JButton btn2 = new JButton("方法 2");
    JButton btn3 = new JButton("方法 3");
    Cat cat = new Cat();
    public static void main(String[] args) 
    {
        Demo1 d1 = new Demo1();
    }
    public Demo1()
    {
        //方法1
        this.btn.addActionListener(this);
        //方法2
        this.btn2.addActionListener(
                            new ActionListener()
                            {
                                public void actionPerformed(ActionEvent e) 
                                {
                                        JOptionPane.showInputDialog("Btn2");
                                }
                            }
                            );
        //方法3
        
        this.btn3.addActionListener(this.cat);
                
                this.setLayout(new FlowLayout(FlowLayout.LEFT));
                this.getContentPane().add(this.btn);
                this.getContentPane().add(this.btn2);
                this.getContentPane().add(this.btn3);
                
                this.setVisible(true);
                this.setSize(320,200);
                this.setLocation(500,300);
                this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == btn)
        {
            JOptionPane.showConfirmDialog(this, "Btn");
        }
    }

}
 class Cat implements ActionListener
{
    public void actionPerformed(ActionEvent e)
    {
        JOptionPane.showInputDialog("Btn3");
    }
}