public Integer validateInteger(String name, boolean isRequired) {
        Integer value = get(name);

        if (value == null) {
            if (isRequired)
                throw new ConfigException(name, null, String.format("The OAuth configuration option %s must be non-null", name));
            else
                return null;
        }

        return value;
    }
Validates that, if a value is supplied, is a value that:

<li>
    <ul>is an Integer</ul>
    <ul>has a value that is not less than the provided minimum value</ul>
</li>

If the value is null or an empty string, it is assumed to be an "empty" value and thus
ignored. Any whitespace is trimmed off of the beginning and end.
clients/src/main/java/org/apache/kafka/common/security/oauthbearer/internals/secured/ConfigurationUtils.java