code: public Collection<ContentObserver> getContentObservers(Uri uri) {
      ArrayList<ContentObserver> observers = new ArrayList<>(1);
      for (ContentObserverEntry entry : contentObservers) {
        if (entry.matches(uri)) {
          observers.add(entry.observer);
        }
      }
      return observers;
    }
docs: Returns the content observers registered for updates under the given URI.
  
  Will be empty if no observer is registered.
  
  @param uri Given URI
  @return The content observers, or null