binary search code -:

 void insertInterval(List<int[]> intervals, int left, int right) {

    int lo = 0, hi = intervals.size();

    while (lo < hi) {

        int mid = (lo + hi) / 2;

        if (intervals.get(mid)[0] < left) {

            lo = mid + 1;

        } else {

            hi = mid;

        }

    }

    intervals.add(lo, new int[]{left, right});

}