public Element getElement(int id) {
		switch (id) {
		case ID_NT:
			return nt;
		case ID_PL:
			return pl;
		case ID_WS:
			return ws;
		case ID_CK:
			return ck;
		case ID_MO:
			return mo;
		case ID_SP:
			return sp;
		}
		if (id >= ID_ALA && id <= ID_VAL)
			return aminoAcidElement[id - ID_ALA];
		if (id >= ID_A && id <= ID_U)
			return nucleotideElement[id - ID_A];
		return null;
	}