Java development gui tutorial: jframe listens to form size change events and jframe creates forms

import java.awt.event.WindowEvent;
import java.awt.event.WindowStateListener;
import javax.swing.JFrame;

public class WinFrame extends JFrame {
 public WinFrame(){
  this.setName("Window 窗口状态");
  this.setSize(300,300);
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  this.addWindowStateListener(new WindowStateListener () {
   public void windowStateChanged(WindowEvent state) {

    if(state.getNewState() == 1 || state.getNewState() == 7) {
     System.out.println("窗口最小化");
    }else if(state.getNewState() == 0) {
     System.out.println("窗口恢复到初始状态");
    }else if(state.getNewState() == 6) {
     System.out.println("窗口最大化");
    }
   }
  });
  this.setVisible(true);
 }
 public static void main(String[] args) {
  new WinFrame();
 }
}

public class Test(){
    public static void main(String[] args){
  JFrame frame = new JFrame();
  JPanel panel = new JPanel();
  JTextArea textArea = new JTextArea();

  panel.setLayout(new GridLayout());
  textArea.setText("test");
  //当TextArea里的内容过长时生成滚动条
  panel.add(new JScrollPane(textArea));
  frame.add(panel);

  frame.setSize(200,200);
  frame.setVisible(true);
 }
}