private boolean isSciNumOrOperator(String expression) {

        //First set to true.
        boolean onlySciNot = true;

        //Check for any +, - used not for Scientific notation
        //or not to represent a negative value.
        for (int i = 1; i < expression.length(); i++) {
            //+ or - not following an E.
            if ((expression.charAt(i) == '+' || expression.charAt(i) == '-')
                    && expression.charAt(i - 1) != 'E'
                    && !isOperator(expression.charAt(i - 1))) {

                return false;
            }
        }

        return onlySciNot;
    }