論如何不用四則運算、for循環實現1-n的和

完成這道題目，需要兩部：
1、處理加法運算
2、用遞歸處理for循環
public static int getSum(int upper) {
// if (upper > 0) {
// if (upper == 1) {
// return 1;
// } else {
// //return upper += getSum(upper - 1);
// return upper = addFun(upper,getSum(upper - 1));
// }
// }
// return -1;
//使用三目運算符簡化代碼
// return upper > 0 ? (upper == 1 ? 1 : (upper += getSum(upper - 1))) : -1;
return upper > 0 ? (upper == 1 ? 1 : (upper = addFun(upper,getSum(upper - 1)))) : -1;
}
public static int addFun(int a,int b){
int sum;
int carry;
do{
sum = a^b;
carry = (a&b)<<1;
a = sum;
b = carry;
}
while(carry != 0);
return sum;
}