JAva 2つの大数を乗算

分析は元のブログを参照し、コード整理(注釈と説明)は以下の通りである.
https://blog.csdn.net/outsanding/article/details/79472376

package com.interview.algorithm;

public class Mutiply {
    public static String multiply(String num1, String num2){
        //      char  
        char chars1[] = num1.toCharArray();
        char chars2[] = num2.toCharArray();
        //              ， ：                              。

        int result[] = new int[chars1.length + chars2.length];
        int n1[] = new int[chars1.length];
        int n2[] = new int[chars2.length];


        // char   int  。
        for (int i = 0; i < chars1.length; i++) {
            n1[i] = chars1[i] - '0';
        }
        for (int j = 0; j < chars2.length; j++) {
            n2[j] = chars2[j] - '0';
        }
        //    
        for (int i = 0; i < chars1.length; i++) {
            for (int j = 0; j < chars2.length; j++) {
                result[i + j] += n1[i] * n2[j];
            }
        }
        //        
        for (int i = result.length - 1; i > 0; i--) {
            result[i - 1] += result[i] / 10;
            result[i] = result[i] % 10;
        }
        //  string   ，            ，        
        String resultStr = "";
        for (int i = 0; i < result.length - 1; i++) {
            resultStr += "" + result[i];
        }
        return resultStr;
    }

    public static void main(String[] args) {
        System.out.println(multiply("123","4567"));
    }
}

Stringとintタイプの変換を添付

String s = "123";
int n= 12;
String ss = String.valueOf(n);
int i = Integer.parseInt(s);