protected String concat(final String value, int num) {
        return value.concat(num == 0 ? Pac4jConstants.EMPTY_STRING : "." + num);
    }
<p>concat.</p>

@param value a {@link String} object
@param num a int
@return a {@link String} object
pac4j-config/src/main/java/org/pac4j/config/builder/AbstractBuilder.java