code: public static PropertyBundle load(
          String baseName,
          Locale locale
      ) {
  
          if (baseName.isEmpty()) { // includes NPE-check
              throw new IllegalArgumentException("Base name must not be empty.");
          } else if (locale == null) {
              throw new NullPointerException("Missing locale.");
          }
  
          CacheKey cacheKey = new CacheKey(baseName, locale);
          BundleReference bundleRef = CACHE.get(cacheKey);
          PropertyBundle bundle;
  
          if (bundleRef != null) {
              bundle = bundleRef.get();
              bundleRef = null; // helps the GC
              if (bundle != null) {
                  return bundle;
              }
          }
  
          Object ref;
  
          while ((ref = REFERENCE_QUEUE.poll()) != null) {
              CACHE.remove(((BundleReference) ref).cacheKey);
          }
  
          List<PropertyBundle> bundles = new ArrayList<>();
  
          for (Locale candidate : getCandidateLocales(locale)) {
              try {
                  bundle = newBundle(baseName, candidate);
                  if (bundle != null) {
                      bundles.add(bundle);
                  }
              } catch (IOException ioe) {
                  throw new IllegalStateException(ioe);
              }
          }
  
          if (bundles.isEmpty()) {
              throw new MissingResourceException(
                  "Cannot find resource bundle for: " + toResourceName(baseName, locale),
                  PropertyBundle.class.getName(),
                  "");
          }
  
          for (int i = bundles.size() - 1; i >= 1; i--) {
              bundles.set(i - 1, bundles.get(i - 1).withParent(bundles.get(i)));
          }
  
          bundle = bundles.get(0);
          CACHE.putIfAbsent(cacheKey, new BundleReference(bundle, cacheKey));
          return bundle;
  
      }
docs: /*[deutsch]
  <p>Versucht, ein neues Ressourcenb&uuml;ndel zu laden. </p>
  
  @param   baseName    the base name
  @param   locale      the locale containing language, country and variant
  @return  property bundle if successfully loaded
  @throws  MissingResourceException if no bundle could be loaded
  @throws  IllegalArgumentException if the base name is empty