leetcode:Merge Intervals

Given a collection of intervals, merge all overlapping intervals.

For example,
Given [1,3],[2,6],[8,10],[15,18],
return [1,6],[8,10],[15,18].

<span style="font-size:18px;">/**
 * Definition for an interval.
 * public class Interval {
 *     int start;
 *     int end;
 *     Interval() { start = 0; end = 0; }
 *     Interval(int s, int e) { start = s; end = e; }
 * }
 */
public class Solution {
    public ArrayList<Interval> merge(ArrayList<Interval> intervals) {
        Interval pre, next;
        int i = 0;
        Object[] objects = intervals.toArray();
        Arrays.sort(objects, new Comparator(){
           public int compare(Object o1, Object o2){
               Interval i1 = (Interval)o1;
               Interval i2 = (Interval)o2;
               return i1.start - i2.start;
           } 
        });
        ArrayList<Interval> l = new ArrayList<>();
        for(Object o : objects){
            l.add((Interval)(o));
        }
        while(i + 1 < l.size()){
            pre = l.get(i);
            next = l.get(i + 1);
            if(next.start <= pre.end){
                pre.end = Math.max(pre.end, next.end);
                l.remove(i + 1);
            }else{
                ++i;
            }
        }   
        
        return l;
    }
}</span>