java編寫程序,單擊按鈕,改變框架窗口的大小，希望是壹個完整的編程

import java.awt.event.ActionListener;

import javax.swing.JButton;

import javax.swing.JFrame;

public class Jframe extends JFrame {

public Jframe() {

add();

button();

}

public void add() {

this.setSize(300, 200);

this.setLocationRelativeTo(null);

this.setLayout(null);

this.setVisible(true);

}

public void button() {

JButton j = new JButton("點擊");

j.setBounds(99, 66, 60, 30);

j.addActionListener(new ActionListener() {

@Override

public void actionPerformed(ActionEvent arg0) {

Jframe.this.setSize(500, 400);

Jframe.this.repaint();

}

});

this.add(j);

}

public static void main(String[] args) {

new Jframe();

}

}