protected void setStringToPop(String stringToPop) {
		/*
		 * if (!automata.StringChecker.isAlphanumeric(stringToPop)) throw new
		 * IllegalArgumentException("Pop string must "+ "be alphanumeric!");
		 */
		PushdownAutomaton myPDA = (PushdownAutomaton) this.getAutomaton();
		if (myPDA.singleInputPDA && stringToPop.length() > 1){
			throw new IllegalArgumentException("Pop string must have no more than one character!");
		}
		myStringToPop = stringToPop;
	}