【未完待续】Java---超出范围的解决方案

package com.algorithm.java.blueBirdge;

import java.util.Scanner;

public class zero
{
    public static int zero(String a){
        int sum=0;
        for(int i=0;i<a.length();i++){
            char c=a.charAt(i);
            if(c==‘0‘) sum+=1;
        }
        return sum;
    }

    public static String jiech(int n){

        long chengji =1;
        for(int i=1;i<=n;i++){
            chengji=chengji*i;
        }
        String s = String.valueOf(chengji);
        return s;
    }
    public static void main(String[] args){
        Scanner read =new Scanner(System.in);
        int  n=read.nextInt();
        //System.out.println(jiech(11));
        String as=jiech(n);
        System.out.println(zero(as));
    }
}