求JAVA简单计算器代码

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

public class testZ extends JFrame implements ActionListener{
private JPanel jPanel1,jPanel2;
private JTextField resultField;
private JButton s1,s2,s3,s4,s5,s6,s7,s8,s9,s0,b1,b2,b3,b4,f1,f2;
private boolean end,add,sub,mul,div;
private String str;
private double num1,num2;

public testZ(){
super("计算器");
setSize(300,240);
Container con=getContentPane();
con.setLayout(new BorderLayout());
jPanel1=new JPanel();
jPanel1.setLayout(new GridLayout(1,1));
jPanel2=new JPanel();
jPanel2.setLayout(new GridLayout(4,4));
resultField=new JTextField("0");
jPanel1.add(resultField);
con.add(jPanel1,BorderLayout.NORTH);
s1=new JButton(" 1 "); s1.addActionListener(this);
s2=new JButton(" 2 "); s2.addActionListener(th