public static int indexOfDifference(CharSequence cs1, CharSequence cs2) {
		if (cs1 == cs2) {
			return INDEX_NOT_FOUND;
		}
		if (cs1 == null || cs2 == null) {
			return 0;
		}
		int i;
		for (i = 0; i < cs1.length() && i < cs2.length(); ++i) {
			if (cs1.charAt(i) != cs2.charAt(i)) {
				break;
			}
		}
		if (i < cs2.length() || i < cs1.length()) {
			return i;
		}
		return INDEX_NOT_FOUND;
	}