java求和1+2+3+…+n

1, 常规实现

public int Sum_Solution1(int n) {
		int sum = 0;
	    for (int i = 1; i <= n; i++) {
			sum += i;
		}
	    return sum;
	}

2, 递归实现

思路：巧用递归 --> 运用&&的短路特性

public int Sum_Solution2(int n) {
	    int sum = n;
	    boolean result = (n > 0) && ((sum += Sum_Solution(n-1)) > 0);//n<=0时跳出递归
	    return sum;
	}