help with concurrent modification exception

[jdgallag]

I am sort of new to java, and I want to do things in a semi-functionaly way, just for fun. So I wrote a small library of static methods for listoperations, a functional style insertion sort, and then I got stuck on merge sort. I have written merge sort before in java, but I wanted to do it in a functional way. In the code I am going to paste below, I am almost certain that merge is working correctly. I have tested it up and down, with manually created lists. I am also certain that halve works correctly. All methods are static. The code I have for mergeSort is:

public static <t extends Comparable<t>> List<t> mergeSort(List<t> list){
		//System.out.println("hhh");
		//if (list.isEmpty()){
		//	List<t> empty = new LinkedList<t>();
		//	return empty;
		//}
		if(list.size() <= 1){//was else if
		//	System.out.println("aahhhh");
			return list;
		}
		else{
			//System.out.println("mmm");
			Pair<List<t>> pair = ListOps.halve(list);
			List<t> firstH = mergeSort(pair.fst());
			List<t> lastH = mergeSort(pair.snd());
			return merge2(firstH,lastH);
			
		}
		
		
	}

And I get concurrent modification exception. I am not using threads.

[jdgallag]

No problem. I was playing with a list in a static main class, that was being thrown all over the place. When I tested with real tests, everything works great.