通过子方法随机生成四则运算

package kgh;

import java.util.Random;
import java.util.Scanner;
public class ghj {
public static void main(String[] args)
{
int sum = 0;
Scanner sc = new Scanner(System.in);
System.out.println("请输入操作数个数：");
int caozuo = sc.nextInt();
System.out.println("请输入式子个数：");
int shizi = sc.nextInt();
String [] arr = new String[shizi];

for(int i=0;i<shizi;i++)
{
String s = chuti(caozuo);
while(panduan(arr,s))
{
s=chuti(caozuo);
}
arr[sum] = s;
sum++;
}

}

public static boolean panduan(String arr[],String b)//判断是否重复
{
for(int i=0;i<arr.length;i++)
{
if(b.equals(arr[i]))
{
return true;
}
}
return false;
}

public static String chuti(int d)//随机生成式子
{
String a="";
String [] b = {"+","-","/","*"};
Random ra = new Random();
for(int i=0;i<(d+1);i++)
{
if(i<d)
{
a+=ra.nextInt(10);
int t = ra.nextInt(4);
a+=b[t];
}else
{
a+=ra.nextInt(10);
}
}
a+="=";
System.out.println(a);
return a;
}

}