Insert Interval

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

You may assume that the intervals were initially sorted according to their start times.

Example 1:
Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9].

Example 2:
Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as [1,2],[3,10],[12,16].

This is because the new interval [4,9] overlaps with [3,5],[6,7],[8,10].

Idea: Easy question. Linear visiting.

/**
 * 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> insert(ArrayList<Interval> intervals, Interval newInterval) {
        // Start typing your Java solution below
        // DO NOT write main() function
        boolean merge = false;
        for (int i=0; i<intervals.size(); i++) {
            Interval inv = intervals.get(i);
            if (newInterval.start <= inv.start && newInterval.end >= inv.start) {
                merge = true;
                inv.start = newInterval.start;
            }
            
            else if (newInterval.start <= inv.end && newInterval.start >= inv.start) {
                merge = true;
            }
            
            
            if (merge) {
                //find end
                for (int j = i; j<intervals.size(); j++) {
                    inv = intervals.get(j);
                    if (inv.end >= newInterval.end) {
                        break;
                    }
                    else if (j+1 < intervals.size() && newInterval.end <= intervals.get(j+1).start) {
                        inv.end = newInterval.end;
                        break;
                    }
                    else if (j+1 >= intervals.size()) {
                        inv.end = newInterval.end;
                        break;
                    }
                    else {
                        if (j+1 < intervals.size()) {
                            inv.end = intervals.get(j+1).start;
                        }
                    }
                }
                break;
            }
            else {
                if (newInterval.start > inv.end && i+1 < intervals.size() &
                           & intervals.get(i+1).start > newInterval.end) {
                    intervals.add(i+1, newInterval);
                    return intervals;
                }
                else if (newInterval.start > inv.end && i+1 == intervals.size()) {
                    intervals.add(newInterval);
                    return intervals;
                }
                else if (newInterval.end < inv.start) {
                    intervals.add(i, newInterval);
                    return intervals;
                }
            }
        }
        
        ArrayList<Interval> result = new ArrayList<Interval>();
        if (merge) {
            for (int i=0; i<intervals.size(); i++) {
                Interval inv = intervals.get(i);
                result.add(inv);
                for (int j=i+1; j<intervals.size(); j++) {
                    if (inv.end == intervals.get(j).start) {
                        inv.end = intervals.get(j).end;
                        i = j;
                    }
                }
            }
        }
        else {
            if (intervals.size() == 0) {
                intervals.add(newInterval);
            }
            return intervals;
        }
        return result;
    }
}