Minimum Size Subarray Sum

public class Solution {
    public int minSubArrayLen(int s, int[] nums) {
        // http://bookshadow.com/weblog/2015/05/12/leetcode-minimum-size-subarray-sum/
        // O(n)
        int m=nums.length+1, sum=0, len =nums.length, l=0, r=0;
        if(nums==null||nums.length==0) return 0;
        while(true){
            if(sum<s){
                if(r>=len)
                    break;
                sum+=nums[r];
                r++;
            }else{
                if(l>r)
                    break;
                m = Math.min(m,r-l);
                sum -= nums[l];
                l++;
            }
        }
        return m<=len? m:0;
        
        
    }
    
}