public String manual()
    {
        int commandLength = validCommands.size();
        String commands = "";
        int wordCount;

        for(int i = 0;i < commandLength;++i) {
            wordCount = i + 1;
            commands += wordCount + " word commands:\n";

            for(String command : validCommands.get(i)) {
                commands += " | " + command;
            }
            commands += " |" + (!(i < commandLength - 1) ? "" : "\n");
        }

        return commands;
    }