private char replacement;

    public ProlongedSoundMarkCharFilterFactory(final IndexSettings indexSettings, final Environment env, final String name,
            final Settings settings) {
        super(indexSettings, name);
        final String value = settings.get("replacement");
        if (value == null || value.length() == 0) {
            replacement = '\u30fc';
        } else {

     *
     * @param target The target string.
     * @param replacement The replacement string.
     */
    public void add(final String target, final String replacement) {
        if (target == null || replacement == null) {
            throw new CrawlerSystemException("Target or replacement cannot be null.");
        }
        convertMap.put(target, replacement);
    }

    /**
     * Sets the conversion map.