learn how to create a comparator

Merge Intervals.java

/**
 * 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) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ArrayList<Interval> result=new ArrayList<Interval>(); 
        if(intervals.size()==0) return result;     
        
    Comparator<Interval> INTERVAL_ORDER=new Comparator<Interval>()
	{
       @Override
	public int compare(Interval i, Interval j)
	{
        return new Integer(i.start).compareTo(new Integer(j.start));   
        }
	}; 
    
    Collections.sort(intervals, INTERVAL_ORDER);
    int s=intervals.get(0).start; 
    int e=intervals.get(0).end;
    result.add(intervals.get(0));
	for(int i=1; i<intervals.size(); i++)
	{
	if(intervals.get(i).start>=s && intervals.get(i).start<=e)
	{
		result.remove(result.size()-1);
		e=Math.max(e, intervals.get(i).end);		
	}else
	{
		s=intervals.get(i).start; e=intervals.get(i).end;
	}
	result.add(new Interval(s, e));
	}
        return result; 
    }
}