611 Valid Triangle Number

class Solution {
    public int triangleNumber(int[] nums) {
        int ans = 0;
        if (nums == null || nums.length < 3) return ans;

        Arrays.sort(nums);

        for (int k = 2; k < nums.length; k++){
            int i = 0, j = k - 1;

            while (i < j){
                if (nums[i] + nums[j] > nums[k]){
                    ans += j - i;
                    j--;
                }
                else{
                    i++;
                }
            }
        }

        return ans;
    }
}