private static boolean isValidAdditionalInputCommand(String input)
    {
        //grab the command
        char option = input.charAt(0);
        
        if(input.length() > 1)
        {
            //all add'l command require whitespace after initial char
            if(!Character.isWhitespace(input.charAt(1)))
                return false;
            
            //trim the add'l data
            String seq = input.substring(1).trim();
            
            //The r command MUST have an add'l data length of 1
            //corresponding to one character
            if(seq.length() > 1 && option == 'r')
                return false;
            
            //if there is no add'l data -> not valid
            if(seq.length() < 1)
                return false;
            
            //attempt to parse add'l data if jump command
            //if cannot parse, then invalid
            if(option == 'j')
            {
                try
                {
                    Integer.parseInt(seq);
                }
                
                catch (NumberFormatException e)
                {
                    return false;
                }
            }
        }
        
        else return false;
        
        //if all tests are passed
        return true;
    }