两大数相加

/** * @param args */ public static void main(String[] args) { BigInt b = new BigInt(); b.add("999999999999444599999999999999999", "99223333333223455559"); } public String add(String a, String b) { // 检查输入 if (!a.matches("//d+") || !a.matches("//d+")) { return null; } final int BASE = 10;// 10进制 int lenA = a.length();// 加数的长度 int lenB = b.length();// 被加数的长度 int maxLen, partialSum, carry = 0;// 大数的长度，和，进位 maxLen = (lenA > lenB) ? lenA : lenB; StringBuffer sum = new StringBuffer(); int temA, temB = 0; for (int i = 0; i < maxLen; i++) { if (i >= lenA) { temA = 0; } else { temA = Integer.valueOf(a.charAt(lenA - i - 1) - 48); } if (i >= lenB) { temB = 0; } else { temB = Integer.valueOf(b.charAt(lenB - i - 1) - 48); } partialSum = temA + temB + carry; carry = partialSum / BASE; sum.append(partialSum % BASE); } if (carry == 1) sum.append(carry); System.out.println(a + " + " + b + " = " + sum.reverse().toString()); return sum.reverse().toString(); }