class JsonUtil {

    /**
     * Private constructor.
     */
    private JsonUtil() { }

    public static JsonObjectBuilder add(final JsonObjectBuilder builder, final String key, final String value) {
        if (value != null) {
            builder.add(key, value);
        }
        return builder;
    }

    public static JsonObjectBuilder add(final JsonObjectBuilder builder, final String key, final BigInteger value) {<FILL_FUNCTION_BODY>}

    public static JsonObjectBuilder add(final JsonObjectBuilder builder, final String key, final BigDecimal value) {
        if (value != null) {
            builder.add(key, value);
        }
        return builder;
    }

    public static JsonObjectBuilder add(final JsonObjectBuilder builder, final String key, final Enum value) {
        if (value != null) {
            builder.add(key, value.name());
        }
        return builder;
    }

    public static ZonedDateTime jsonStringToTimestamp(final String s) {
        if (s == null) {
            return null;
        }
        try {
            return ZonedDateTime.parse(s);
        } catch (DateTimeParseException e) {
            return null;
        }
    }

}

        if (value != null) {
            builder.add(key, value);
        }
        return builder;
    
<no_super_class>