不用加减乘除做加法

 public int Add(int num1,int num2) {
        if(num1 == 0 && num2==0) return 0;
        if(num1 !=0 &&num2==0) return num1;
        if(num1==0&&num2!=0) return num2;
        int sum=0;
        int carray=0;
        do{
          sum = num1^num2;
          carray = (num1&num2)<<1;
          num1 = sum;
          num2 = carray;
        }while(num2!=0);
         return sum;
    }