private void verifyInt(String id, String val) {
        try {
            verifyInt(id, Integer.parseInt(val));
        } catch (NumberFormatException e) {
            ConfigDefinition.defFail(id, val, "int", e);
        }
    }
Throws if the given value is not legal
config/src/main/java/com/yahoo/vespa/config/ConfigDefinition.java