描写叙述：

Given two numbers represented as strings, return multiplication of the numbers as a string.

Note: The numbers can be arbitrarily large and are non-negative.

思路：

简而言之，要实现的就是BigInteger(a).Multiply(BigInteger(b))的功能，但非常显然，leetcode中不让用BigInteger

代码：

public class Solution { public  String multiply(String num1, String num2)	{		if(num1==null||num2==null)			return new String();		num1=num1.trim();		num2=num2.trim();		if(num1.equals("0")||num2.equals("0"))			return "0";	   List
     
      listNum1=new ArrayList<>();	   List
      
       listNum2=new ArrayList<>();	   List
       
        listResult=new ArrayList<>();	   int len1=num1.length();	   int len2=num2.length();	   int i=0,j=0,lenResult=0,index=0;	   int baseNum=0,flowNum=0,tempNum1=0,tempNum2=0;	   for( i=len1-1;i>=0;i--)		   listNum1.add(num1.charAt(i)-'0');	   for( i=len2-1;i>=0;i--)		   listNum2.add(num2.charAt(i)-'0');	   tempNum2=listNum2.get(0);	   for(i=0;i