code: public static void setInitializer(ZoneRulesInitializer initializer) {
          if (INITIALIZED.get()) {
              throw new IllegalStateException("Already initialized");
          }
          if (!INITIALIZER.compareAndSet(null, initializer)) {
              throw new IllegalStateException("Initializer was already set, possibly with a default during initialization");
          }
      }
docs: Sets the initializer to use.
  <p>
  This can only be invoked before the {@link ZoneRulesProvider} class is loaded.
  Invoking this method at a later point will throw an exception.
  
  @param initializer  the initializer to use
  @throws IllegalStateException if initialization has already occurred or another initializer has been set