这是一个简易计算器，设置四个按钮代表加减乘除，然后三个文本框，前两个文本框输入，第三个文本框显示结果，帮我改一下

package text2;

public class Calculator {
public static void main(String[] args) {
WindowCalculator win = new WindowCalculator();
win.setTitle("计算");
}
}

package text2;

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

public class WindowCalculator extends JFrame implements DocumentListener{
JTextArea t

```bash

Button button1,button2,button3,button4;
Panel panel = new Panel();
 
 
 
WindowCalculator(){
 
    text1 = new JTextArea(8,8);
    text2 = new JTextArea(8,8);
    text3 = new JTextArea(8,8);
    
    add(text1);
    add(text2);
    add(text3);
    text1.setLineWrap(true);
    text2.setLineWrap(true);
    text3.setLineWrap(true);
    text3.setEditable(false);
    (text1.getDocument()).addDocumentListener(this);
    (text2.getDocument()).addDocumentListener(this);
    (text3.getDocument()).addDocumentListener(this);
 
 
    JButton button1 = new JButton("加法运算");
    JButton button2 = new JButton("减法运算");
    JButton button3 = new JButton("乘法运算");
    JButton button4 = new JButton("除法运算");
    panel.add(button1);
    panel.add(button2);
    panel.add(button3);
    panel.add(button4);
    add(panel);
    
    setLayout(new FlowLayout());
    setBounds(320,200,700,400);
    setVisible(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
 
    button1.addActionListener((ActionListener) this);
    button2.addActionListener((ActionListener) this);
    button3.addActionListener((ActionListener) this);
    button4.addActionListener((ActionListener) this);
}
 
 
public void insertUpdate(DocumentEvent e) {
    try{
    double A = Double.parseDouble(text1.getText());
    double B = Double.parseDouble(text2.getText());
    double result = 0;
    
       if (panel.equals("button1")){
          result = A + B;
       }
       else if (panel.equals("button2")){
           result = A - B;
       }
       else if (panel.equals("button3")){
           result = A * B;
       }
       else if (panel.equals("button4")){
           result = A / B;
       }
    text3.append("结果是：" + result);
   }
   catch(Exception exp){
       text3.append("字符错误，请删除后重新输入：");
   }
    
}
 
 
public void removeUpdate(DocumentEvent e) {
    
    changedUpdate(e);
}
 
 
public void changedUpdate(DocumentEvent e) {
    changedUpdate(e);
}
}

```css

那个bass 和css是因为我写的这个有问题发布到平台上随便加的