@Override
        public void ensureValid(final String name, final Object value) {
            @SuppressWarnings("unchecked")
            List<String> values = (List<String>) value;
            for (String string : values) {
                validString.ensureValid(name, string);
            }
        }
A numeric range that checks both the upper (inclusive) and lower bound
clients/src/main/java/org/apache/kafka/common/config/ConfigDef.java