minimum size subarray sum

public class Eight{
    public static void main(String[] args){
        System.out.println(minSubArrayLen(7, new int[]{2,3,1,2,4,3}));
    }

    //s > 0, and any element in nums are bigger than zero
    public static int minSubArrayLen(int s, int[] nums){
        if (nums == null || nums.length == 0){
            return 0;
        }

        int length = 0;
        int sum = 0;
        int leftPos = 0;
        int rightPos = 0;
        while (rightPos <= nums.length){
            if (sum >= s){
                length = length == 0 ? rightPos - leftPos : Math.min(length, rightPos - leftPos);
                sum -= nums[leftPos++];
            }else{
                if (rightPos == nums.length){
                    break;
                }
                sum += nums[rightPos++];
            }
        }

        return length;
    }
}