code: private static boolean initCache() {
          if (CHRONOS_BY_ID.get("ISO") == null) {
              // Initialization is incomplete
  
              // Register built-in Chronologies
              /* /* J2ObjC removed: Only "gregorian" and "julian" calendars are supported.
              registerChrono(HijrahChronology.INSTANCE);
              registerChrono(JapaneseChronology.INSTANCE);
              registerChrono(MinguoChronology.INSTANCE);
              registerChrono(ThaiBuddhistChronology.INSTANCE); */
  
              // Register Chronologies from the ServiceLoader
              @SuppressWarnings("rawtypes")
              ServiceLoader<AbstractChronology> loader =  ServiceLoader.load(AbstractChronology.class, null);
              for (AbstractChronology chrono : loader) {
                  String id = chrono.getId();
                  if (id.equals("ISO") || registerChrono(chrono) != null) {
                      // Log the attempt to replace an existing Chronology
                      PlatformLogger logger = PlatformLogger.getLogger("java.time.chrono");
                      logger.warning("Ignoring duplicate Chronology, from ServiceLoader configuration "  + id);
                  }
              }
  
              // finally, register IsoChronology to mark initialization is complete
              registerChrono(IsoChronology.INSTANCE);
              return true;
          }
          return false;
      }
docs: Initialization of the maps from id and type to Chronology.
  The ServiceLoader is used to find and register any implementations
  of {@link java.time.chrono.AbstractChronology} found in the bootclass loader.
  The built-in chronologies are registered explicitly.
  Calendars configured via the Thread's context classloader are local
  to that thread and are ignored.
  <p>
  The initialization is done only once using the registration
  of the IsoChronology as the test and the final step.
  Multiple threads may perform the initialization concurrently.
  Only the first registration of each Chronology is retained by the
  ConcurrentHashMap.
  @return true if the cache was initialized