code: private static void registerProvider0(ZoneRulesProvider provider) {
          for (String zoneId : provider.provideZoneIds()) {
              Jdk8Methods.requireNonNull(zoneId, "zoneId");
              ZoneRulesProvider old = ZONES.putIfAbsent(zoneId, provider);
              if (old != null) {
                  throw new ZoneRulesException(
                      "Unable to register zone as one already registered with that ID: " + zoneId +
                      ", currently loading from provider: " + provider);
              }
          }
      }
docs: Registers the provider.
  
  @param provider  the provider to register, not null
  @throws ZoneRulesException if unable to complete the registration