java实现大数据相乘

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.util.Random;

public class Bignum {
static int Num;
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
System.out.println("请输入你想要的两位大数长度：");
BufferedReader br1=new BufferedReader(new InputStreamReader(System.in));
Num = Integer.parseInt(br1.readLine().toString()); 
//判断是否输入为0
if (Num==0){
System.out.println("两数相乘,积=0");
}else{
//生产指定位数的随机数   两个大数
String random01 =RandomNum(Num);
String random02 =RandomNum(Num);
String totile;
//大数据相乘
totile=getMultiply(random01,random02);
System.out.println("第一个乘数长度："+random01);
System.out.println("第二个乘数长度："+random02);
System.out.println("两位大数相乘积:"+totile);
}
}
//两个大数相乘
 public static String getMultiply(String Str1,String Str2){