private boolean isValidEmpNum(String employeeNumber){
        
        boolean isValid = false;
        
        if(employeeNumber.length() != 3){
            return false;
        }else{
            for(int i = 0;i < employeeNumber.length(); i++){
                if(Character.isDigit(employeeNumber.charAt(i)))
                    isValid = true;
                else
                    return false;
            }
        }
        
        
        return isValid;
            
    }