Generic Combination implementation in java

Combinations.java

import java.util.ArrayList;
import java.util.Iterator;
import java.util.NoSuchElementException;


public class Combinations<T> implements Iterable<ArrayList<T>> {

	private int totalCombinations;
	private int n, r;
	private int factorial(int n) {
		int p = 1;
		for (int i = n; i > 1; i--) {
			p *= i;
		}
		return p;
	}
	private ArrayList<T> seq;
	
	public Combinations(ArrayList<T> sequence, int r) {
		this.r = r;
		seq = sequence;
		n = sequence.size();
		int num = 1;
		for (int i = n, j = n - r + 1; i >= j; i--) {
			num *= i;
		}
		totalCombinations = num / factorial(r);		
	}
	
	@Override
	public Iterator<ArrayList<T>> iterator() {		
		return new CombinationIterator();
	}	
	
	private class CombinationIterator implements Iterator<ArrayList<T>> {
		private int count = 0;
		private int[] pos;
		
		private CombinationIterator() {			
			pos = new int [r];
			for (int i = 0; i < r; i++) {
				pos[i] = i;
			}
		}
		@Override
		public boolean hasNext() {
			
			return count < totalCombinations;
		}

		@Override
		public ArrayList<T> next() {
			int l, m;
			if(!hasNext())
				throw new NoSuchElementException();
			ArrayList<T> combination = makeList();
			//computing for next iteration
			int k = r - 1;
			if (pos[k] + 1 < n) {
				pos[k]++;
			}
			else {
				l = k - 1;
				while (l >= 0) {
					if (pos[l] + 1 < n - r + (l + 1)) {
						pos[l]++;
						m = l + 1;
						while (m <= k) {
							pos[m] = pos[m-1] + 1;
							m++;
						}
						break;
					}
					l--;
				}
			}
			count++;
			return combination;
		}
		
		private ArrayList<T> makeList(){
			ArrayList<T> list = new ArrayList<T>();
			for(int i = 0; i < r; i++) {
				list.add(seq.get(pos[i]));
			}
			return list;
		}
	}
	
	public static void main(String[] args){
		//Making a combination sequence out of strings...
		String test1 = "abcde";
		ArrayList<Character> converted = new ArrayList<Character>();
		for (int i = 0; i < test1.length(); i++) {
			converted.add(test1.charAt(i));			
		}
		
		Combinations<Character> combCharacter 
			= new Combinations<Character>(converted, 3);
		
		for (ArrayList<Character> arrayList : combCharacter) {
			for (Character character : arrayList) {
				System.out.print(character);
			}
			System.out.println();
		}	
		
	}
}