java 模拟四则运算软件

//写这个程序也为了纪念王江民先生……话说当年他也是写过这个类似程序
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class game extends Applet implements ActionListener{
    //定义变量
    int num1, num2, num3, jieguo, jilu, error = 0, right = 0, key = 0;
    char op;
    float percent = 0;
    String res, lev;
    Image labmag;
    AudioClip audio1, audio2;
    Label prompt1,prompt2;
    TextField qus, ans, info;
    Button next, enter, record;
    public void init()
    {
        //初始化图片
        labmag = getImage (getCodeBase(),"1.jpg");
        //初始化音乐
        audio1 = getAudioClip(getDocumentBase(),"Error.au");
        audio2 = getAudioClip(getDocumentBase(),"Right.au");
        qus = new TextField(15);
        //初始化按钮，文本框
        ans = new TextField(10);
        info = new TextField(30);
        enter = new Button("确定");
        next = new Button("新题目");
        record = new Button("记录");
        prompt1 = new Label("问题:");
        prompt2 = new Label("结果:");
        //建立按钮和文本框
        add(prompt1);
        add(qus);
        add(