code: private static void verify(boolean check, String zoneId, String message) {
          if (!check) {
              throw new ZoneRulesException(
                      String.format("Failed verification of zone %s: %s", zoneId, message));
          }
      }
docs: Verify an assumption about the zone rules.
  
  @param check
  {@code true} if the assumption holds, {@code false} otherwise.
  @param zoneId
  Zone ID for which to check.
  @param message
  Error description of a failed check.
  @throws ZoneRulesException
  If and only if {@code check} is {@code false}.