0986 Interval List Intersections

Question

My Solution:

class Solution {
    public int[][] intervalIntersection(int[][] firstList, int[][] secondList) {
        if(firstList.length == 0
          || secondList.length == 0){
            return new int[0][0];
        }
        
        int i = 0;
        int j = 0;
        int startMax = 0;
        int endMin = 0;
        List<int[]> ans = new ArrayList<>();
        
        while(i < firstList.length
             && j < secondList.length){
            startMax = Math.max(firstList[i][0], secondList[j][0]);
            endMin = Math.min(firstList[i][1], secondList[j][1]);
            
            if(endMin >= startMax){
                ans.add(new int[]{startMax, endMin});
            }
            
            if(endMin == firstList[i][1]){
                i++;
            }
            if(endMin == secondList[j][1]){
                j++;
            }
        }
        return ans.toArray(new int[ans.size()][2]);
    }
}