Write a function that add two numbers A and B. You should not use + or any arithmetic operators.

分析：

典型的Bit Operation.

1 class Solution { 2     /* 3      * param a: The first integer 4      * param b: The second integer 5      * return: The sum of a and b 6      */ 7     public int aplusb(int a, int b) { 8         if (a == 0) return b; 9         int sum = a ^ b;10         int carry = (a & b) << 1;11         return aplusb(carry, sum);12     }13 };