用JAVA实现四则运算

//产生随机的四则运算题目,输入答案,判断正误
import java.util.*;
import java.io.*;
class suanshi{ 
               //产生随机数//
	Random rand=new Random();
//int a=(int)Math.random()*50;
//int b=(int)Math.random()*20;//这样的数每次运行时都是一样的.
//int c=(int)Math.random()*10+1;
//rand.setSeed(long d);
int a=(int)rand.nextInt()/1000000;
int b=(int)rand.nextInt()/1000000;
int c=(int)(rand.nextFloat()*10+1);
public static double sum=0;//一定要声明为static的,否则后面的SUM就会为0
public suanshi(){}
char d;
public suanshi(int k){                         //产生运算符号//
	if(1<=c&&c<=3){
		d='+';
		sum=a+b;
	}
	else
		if(4<=c&&c<=6){
		d='-';
		sum=a-b;
	}
	else
		if(7<=c&&c<=8){
		d='×';
		sum=a*b;
	}
	else {
		d='÷';
		sum=a/b;
	}
	System.out.print("("+a+")"+"  "+d+"  "+"("+b+")"+"=");
	
}
}

class panduan extends suanshi {
	public static double count=0;  
int result;
public static int fens=0;
 panduan(){super(0);}
public int  flag=0;
 panduan(int i){
if(i==sum) {
//if(i==(a+b)) {
		System.out.println("你答对了");
		flag=1;
		fens=fens+1;
		count=count+1;
	}
	else {
		System.out.println("你答错了"+"\n"+"不要放弃"+"\t");
System.out.println("正确答案应该是:"+sum);
		flag=0;
       // fens=fens-1;
        count=count+1;
	}
}
int f0(){
	flag=0;
return flag;
}
int f1(){
	flag=1;
	return flag;
}
}
//主类开始//
public class ceshi extends panduan{
public int i=0;
	String s="";
  ceshi(){
	 try{
		 BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
		 s=in.readLine();
		 i=Integer.parseInt(s);
	 }catch(NumberFormatException e){System.out.println("您输入的数字有误");}
	 catch(IOException w){}
	 panduan p=new panduan(i);
 }
//int fc(){return i;}
 public static void main(String [] args) {
int j=0;
int tt=0;
String ss="";
System.out.println("这是四则运算题!");
System.out.println("***************");
System.out.println("第 "+(int)(count+1)+" 题");
do{
	ceshi t=new ceshi();
	//int pp=t.fc();
	// t.panduan(pp);
try{	System.out.println("输入非1的数继续.输入1推出");

		 BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
		 ss=in.readLine();
		 j=Integer.parseInt(ss);
	 }catch(NumberFormatException e){System.out.println("您输入的数字有误");}
	 catch(IOException w){}
	
	switch(j){
		case 0:
			tt=t.f0();
			System.out.println("==========================");
		System.out.println("第 "+(int)(count+1)+" 题");break;
		case 1:
			tt=t.f1();
			System.out.println("=%=%=%=%=%=%=%=%=%=%=%=%");
			System.out.println("您共做的"+count+"题，"+"其中答对"+fens+"题");
            System.out.println("你的总分为:"+(fens/count)*100);
          System.out.println("下次再努力哦!"+"\n"+"谢谢使用,再见^_^!");
	      System.out.println("*********************");break;
	}
}while(tt==0);
}
}