public void addPolyNodeLast(int coefficient, int exponent){
        //Check to see if exponent is a positive number(-1 = no exponent)
        if(exponent < -1)
            throw new IllegalArgumentException("Exponent must be a positive"
                    + " integer.");
        //Check to see if Polynomial is empty
        if(isEmpty())
            firstNode = new PolyNode(coefficient, exponent, null);
        else{
            PolyNode current = firstNode;
            while(current.getNext() != null)
                current = current.getNext();
            
            current.setNext(new PolyNode(coefficient, exponent, null));
        }
    }