code: public ResourceBundle getResourceBundle(String baseName) {
  //    System.out.println(this + " " + this.locale+" ("+resourceBundles.size()+")");
      ResourceBundle bundle = (ResourceBundle) resourceBundles.get(baseName);
      if(null == bundle) {
        resourceBundles.put(baseName, bundle = findBundle(baseName));
      }
      return bundle;
    }
docs: Get the bundle that is active for this thread. This is done by loading
  either the specified locale based resource bundle and, if that fails, by
  looping through the fallback locales to locate a usable bundle.
  
  @return the resource bundle