1 public String multiply(String num1, String num2) {
 2         if(num1.equals("0")||num2.equals("0")){
 3             return "0";
 4         }
 5         String re = "";
 6         for (int i = 0; i < num1.length(); i++) {
 7             String temp = "";
 8             int in = 0;
 9             for (int j = 0; j < num2.length(); j++) {
10                 int k = (num2.charAt(num2.length() - 1 - j) - ‘0‘)
11                         * (num1.charAt(num1.length() - 1 - i) - ‘0‘) + in;
12                 temp = (k % 10) + temp;
13                 in = k / 10;
14             }
15             if (in > 0) {
16                 temp = in + temp;
17             }
18             if (i == 0) {
19                 re = temp;
20             } else {
21                 String t = "";
22                 int in2 = 0;
23                 for (int m = 1; m <= i; m++) {
24                     t = String.valueOf(re.charAt(re.length() - m)) + t;
25                 }
26                 for (int m = 0; m <= re.length() - 1 - i; m++) {
27                     int k = (temp.charAt(temp.length() - 1 - m) - ‘0‘)
28                             + (re.charAt(re.length() - 1 - i - m) - ‘0‘) + in2;
29                     t = (k % 10) + t;
30                     in2 = k / 10;
31                 }
32                 for (int m = 0; m < temp.length() + i - re.length(); m++) {
33                     int k = (temp.charAt(temp.length() + i - re.length() - m
34                             - 1) - ‘0‘)
35                             + in2;
36                     t = (k % 10) + t;
37                     in2 = k / 10;
38                 }
39                 if (in2 > 0) {
40                     t = in2 + t;
41                 }
42                 re = t;
43             }
44             // System.out.println(temp);
45         }
46         return re;
47     }