addActionListener(this)

addActionListener(this)

看书的时候看到这行代码，觉得很奇怪

不是一般写成

 button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                ...
                name.setText(selectedName);
            }
        });

 要一个ActionListener对象，结果一看

public class YourClass implements ActionListener {
  ... // Other code for your class
  public void actionPerformed(ActionEvent actionEvent) {
    System.out.println('I was selected.');
  }
  // Code within some method
   JButton button = new JButton(...);
   button.addActionListener(this);
  // More code within some method
}

 自己的类都实现了ActionListener，当然就可以addActionListener(this)

不过在YourClass里面如果有很多Button的话，你就得在actionPerformed方法里实现区分它们的方法。