public boolean validateExpression(String expression) throws Exception{
        if(content.getAutomatonType() == AutomatonType.AFD)
            return validateAFDExpression(expression);
        else if(content.getAutomatonType() == AutomatonType.AFN)
            return validateAFNExpression(expression);
        else if(content.getAutomatonType() == AutomatonType.AFNE)
            return validateAFNEExpression(expression);
        else{
            errorMessage = "Can't validate expression: [" + expression+ "], Missing Automaton Type.";
            return false;
        }
    }