public static <A> List<A> filter(Iterable<A> l1,
			F1<A, Boolean> f1) {
		ArrayList<A> list = new ArrayList<A>();
		if (l1 != null) {
			for (A a : l1) {
				if (f1.e(a)) {
					list.add(a);
				}
			}
		}
		return list;
	}