Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -. Example: Given a = 1 and b = 2, return 3. ``` public class Solution { public int getSum(int a, int b) { int result = a ^ b; // 按位加 int carray = (a & b) << 1; // 计算进位 if(carray!=0) return getSum(result,carray); //判断进位与处理 return result; } } ```