1 /**
2 * 两个大数相减，默认没有符号位，且都为正数
3 *
4 * @param a
5 * @param b
6 * @return
7 */
8 public static String bigDigitalSub(String a, String b) {
9 //翻转字符串并转化成数组
10 char[] aArray = new StringBuilder(a).reverse().toString().toCharArray();
11 char[] bArray = new StringBuilder(b).reverse().toString().toCharArray();
12 int aLength = aArray.length;
13 int bLength = bArray.length;
14 //找到最大的位数，两个整数的差的位数小于等于两个整数中的最大位数
15 int maxLength = aLength > bLength ? aLength : bLength;
16 int[] result = new int[maxLength];
17 //判断结果符号
18 char sign = '+';
19 if (aLength < bLength) sign = '-';
20 else if (aLength == bLength) {
21 int i = maxLength - 1;
22 while (i > 0 && aArray[i] == bArray[i])
23 i--;
24 if (aArray[i] < bArray[i])
25 sign = '-';
26 }
27 //开始计算结果集
28 for (int i = 0; i < maxLength; i++) {
29 int aInt = i < aLength ? aArray[i] - '0' : 0;
30 int bInt = i < bLength ? bArray[i] - '0' : 0;
31 if (sign == '-') result[i] = bInt - aInt;
32 else result[i] = aInt - bInt;
33 }
34 //处理结果集，如果结果集中的某一位小于0，则向高位借位，然后将本位加10
35 for (int i = 0; i < maxLength - 1; i++) {
36 if (result[i] < 0) {
37 result[i + 1] -= 1;
38 result[i] += 10;
39 }
40 }
41
42 //处理结果集，转化成真正结果
43 StringBuffer realResult = new StringBuffer();
44 if (sign == '-') realResult.append('-');
45 boolean isBeginning = true;
46 for (int i = maxLength - 1; i >= 0; i--) {
47 if (result[i] == 0 && isBeginning) continue;
48 else isBeginning = false;
49 realResult.append(result[i]);
50 }
51 if (realResult.toString().equals("")) realResult.append('0');
52 return realResult.toString();
53 }
