问在Java中实现事件处理时使用`this`关键字

EN

    import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

class test extends JFrame implements ActionListener {
    JButton someButton;


    test() {
        // create the button
        someButton = new JButton();
        // add it to the frame
        this.add(someButton);
        // adding this class as a listener to the button, if button is pressed 
        // actionPerformed function of this class will be called and an event 
        // will be sent to it 
        someButton.addActionListener(this);
    }   
    public static void main(String args[]) {
        test c = new test();
        c.setDefaultCloseOperation(EXIT_ON_CLOSE);
        c.setSize(300, 300);
        c.setVisible(true);
        c.setResizable(false);
        c.setLocationRelativeTo(null);
    }

    public void actionPerformed(ActionEvent e) {

        if(e.getSource() == someButton)
        {
            JOptionPane.showMessageDialog(null, "you pressed somebutton");
        }
    }
};

class A implements ActionListener{
    Button b;
    A(){
         b1 = new Button();
         b1.addActionListener(this);
    }
}