public interface IndexExportFormatter {

    /**
     * Returns the file extension for this format (e.g. ".html", ".json").
     *
     * @return the file extension including the leading dot
     */
    String getFileExtension();

    /**
     * Returns the default index file name for this format (e.g. "index.html", "index.json").
     *
     * @return the index file name
     */
    String getIndexFileName();

    /**

    /**
     * Creates a new HtmlIndexExportFormatter instance.
     */
    public HtmlIndexExportFormatter() {
        // default constructor
    }

    @Override
    public String getFileExtension() {
        return ".html";
    }

    @Override
    public String getIndexFileName() {
        return "index.html";
    }

    @Override

    /**
     * Creates a new JsonIndexExportFormatter instance.
     */
    public JsonIndexExportFormatter() {
        // default constructor
    }

    @Override
    public String getFileExtension() {
        return ".json";
    }

    @Override
    public String getIndexFileName() {
        return "index.json";
    }

    @Override

         * The checksum extension SHOULD NOT contain dot (".") character.
         * Example: "sha1".
         */
        @Nonnull
        String getFileExtension();

        /**
         * Each invocation of this method returns a new instance of calculator, never {@code null} value.
         */
        @Nonnull
        ChecksumCalculator getCalculator();
    }