protected void addToStoredStrings(String s) {
        if (!storedStrings.containsKey(s)) {
        	Integer index = Integer.valueOf(storedStrings.size());
        	if (debug) debug(
        		"addToStoredStrings(s=", StringUtil.toString(s), ") at index=", index.toString()
        	);
            storedStrings.put(s, index);
        }
    }