Merge Intervals

class Solution {
    
    static class pair implements Comparable<pair> {
        int start, end;
        
        pair(int a, int b){
            this.start = a;
            this.end= b;
        }
        
        public int compareTo(pair other){
            return this.start- other.start;
        }
    }
    
    public int[][] merge(int[][] intervals) {
        int n = intervals.length;
        if (n <= 1) return intervals;
        pair[] records = new pair[n];
        for (int i = 0; i < n; i++) {
            records[i] = new pair(intervals[i][0] , intervals[i][1]);
        }
        Arrays.sort(records);
        
        // for (int i = 0; i < n; i++) 
        //     System.out.println(records[i].start + " " + records[i].end);
        
        int mainStart = records[0].start, mainEnd = records[0].end;
        ArrayList<pair> arr = new ArrayList<>();
        for (int i = 1; i < n; i++) {
            
            if (records[i].start <= mainEnd) {
                mainEnd = Math.max(mainEnd, records[i].end);
                // System.out.println("here");
            } else {
                arr.add(new pair(mainStart, mainEnd));
                mainStart = records[i].start;
                mainEnd = records[i].end;
                // System.out.println("here 2");
            }
        }
        arr.add(new pair(mainStart, mainEnd));
        
        int[][] ans = new int[arr.size()][2];
        for (int i =0; i <arr.size(); i++) {
            // System.out.println(arr.get(i).start + " " + arr.get(i).end);
            ans[i][0] = arr.get(i).start;
            ans[i][1] = arr.get(i).end;
        }
        return ans;
    }
}